add jinja2

After successful installation of gitlab-time-report with

pip install gitlab-time-report

running

python -m gitlab_time_report.time_report

would fail with

Traceback (most recent call last):
  File "/usr/local/lib/python3.7/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/local/lib/python3.7/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/usr/local/lib/python3.7/site-packages/gitlab_time_report/time_report.py", line 5, in <module>
    from gitlab_time_report import gitlab_project, template_renderer
  File "/usr/local/lib/python3.7/site-packages/gitlab_time_report/template_renderer.py", line 3, in <module>
    from jinja2 import Environment, FileSystemLoader
ModuleNotFoundError: No module named 'jinja2'

unless the user has otherwise installed jinja2 (e.g. by manually running pip install jinja2).

This was probably not noticed during development, because we already had jinja2 as an (indirect) dev dependency, pulled in by sphinx 3.0.3:

output of poetry show --tree before this change. (6ea3a36a)

black 19.10b0 The uncompromising code formatter.
├── appdirs *
├── attrs >=18.1.0
├── click >=6.5
├── pathspec >=0.6,<1
├── regex *
├── toml >=0.9.4
└── typed-ast >=1.4.0
flake8 3.7.9 the modular source code checker: pep8, pyflakes and co
├── entrypoints >=0.3.0,<0.4.0
├── mccabe >=0.6.0,<0.7.0
├── pycodestyle >=2.5.0,<2.6.0
└── pyflakes >=2.1.0,<2.2.0
isort 4.3.21 A Python utility / library to sort Python imports.
matplotlib 3.2.1 Python plotting package
├── cycler >=0.10
│   └── six * 
├── kiwisolver >=1.0.1
├── numpy >=1.11
├── pyparsing >=2.0.1,<2.0.4 || >2.0.4,<2.1.2 || >2.1.2,<2.1.6 || >2.1.6
└── python-dateutil >=2.1
    └── six >=1.5 
pytest 5.4.1 pytest: simple powerful testing with Python
├── atomicwrites >=1.0
├── attrs >=17.4.0
├── colorama *
├── importlib-metadata >=0.12
│   └── zipp >=0.5 
├── more-itertools >=4.0.0
├── packaging *
│   ├── pyparsing >=2.0.2 
│   └── six * 
├── pluggy >=0.12,<1.0
│   └── importlib-metadata >=0.12 
│       └── zipp >=0.5 
├── py >=1.5.0
└── wcwidth *
python-gitlab 2.2.0 Interact with GitLab API
└── requests >=2.22.0
    ├── certifi >=2017.4.17 
    ├── chardet >=3.0.2,<4 
    ├── idna >=2.5,<3 
    └── urllib3 >=1.21.1,<1.25.0 || >1.25.0,<1.25.1 || >1.25.1,<1.26 
sphinx 3.0.3 Python documentation generator
├── alabaster >=0.7,<0.8
├── babel >=1.3
│   └── pytz >=2015.7 
├── colorama >=0.3.5
├── docutils >=0.12
├── imagesize *
├── jinja2 >=2.3
│   └── markupsafe >=0.23 
├── packaging *
│   ├── pyparsing >=2.0.2 
│   └── six * 
├── pygments >=2.0
├── requests >=2.5.0
│   ├── certifi >=2017.4.17 
│   ├── chardet >=3.0.2,<4 
│   ├── idna >=2.5,<3 
│   └── urllib3 >=1.21.1,<1.25.0 || >1.25.0,<1.25.1 || >1.25.1,<1.26 
├── setuptools *
├── snowballstemmer >=1.1
├── sphinxcontrib-applehelp *
├── sphinxcontrib-devhelp *
├── sphinxcontrib-htmlhelp *
├── sphinxcontrib-jsmath *
├── sphinxcontrib-qthelp *
└── sphinxcontrib-serializinghtml *
sphinx-rtd-theme 0.4.3 Read the Docs theme for Sphinx
└── sphinx *
    ├── alabaster >=0.7,<0.8 
    ├── babel >=1.3 
    │   └── pytz >=2015.7 
    ├── colorama >=0.3.5 
    ├── docutils >=0.12 
    ├── imagesize * 
    ├── jinja2 >=2.3 
    │   └── markupsafe >=0.23 
    ├── packaging * 
    │   ├── pyparsing >=2.0.2 
    │   └── six * 
    ├── pygments >=2.0 
    ├── requests >=2.5.0 
    │   ├── certifi >=2017.4.17 
    │   ├── chardet >=3.0.2,<4 
    │   ├── idna >=2.5,<3 
    │   └── urllib3 >=1.21.1,<1.25.0 || >1.25.0,<1.25.1 || >1.25.1,<1.26 
    ├── setuptools * 
    ├── snowballstemmer >=1.1 
    ├── sphinxcontrib-applehelp * 
    ├── sphinxcontrib-devhelp * 
    ├── sphinxcontrib-htmlhelp * 
    ├── sphinxcontrib-jsmath * 
    ├── sphinxcontrib-qthelp * 
    └── sphinxcontrib-serializinghtml * 
sphinxcontrib.spelling 5.0.0 Sphinx spelling extension
├── pyenchant >=1.6.5
├── six *
└── sphinx >=2.0.0
    ├── alabaster >=0.7,<0.8 
    ├── babel >=1.3 
    │   └── pytz >=2015.7 
    ├── colorama >=0.3.5 
    ├── docutils >=0.12 
    ├── imagesize * 
    ├── jinja2 >=2.3 
    │   └── markupsafe >=0.23 
    ├── packaging * 
    │   ├── pyparsing >=2.0.2 
    │   └── six * 
    ├── pygments >=2.0 
    ├── requests >=2.5.0 
    │   ├── certifi >=2017.4.17 
    │   ├── chardet >=3.0.2,<4 
    │   ├── idna >=2.5,<3 
    │   └── urllib3 >=1.21.1,<1.25.0 || >1.25.0,<1.25.1 || >1.25.1,<1.26 
    ├── setuptools * 
    ├── snowballstemmer >=1.1 
    ├── sphinxcontrib-applehelp * 
    ├── sphinxcontrib-devhelp * 
    ├── sphinxcontrib-htmlhelp * 
    ├── sphinxcontrib-jsmath * 
    ├── sphinxcontrib-qthelp * 
    └── sphinxcontrib-serializinghtml *