Make sure all files are bundled correctly

[standage]

Updated setup.py and MANIFEST.in to make sure all relevant code and files are bundled with the package. Closes #12.

Confirmed with the following.

conda create --name TESTENV -y python=3.7 pytest pytest-cov
conda activate TESTENV
pip install git+https://github.com/bioforensics/lusSTR.git@fixfiles
pytest --cov=lusSTR --pyargs lusSTR
ls -lhp ~/anaconda3/envs/TESTENV/lib/python3.7/site-packages/lusSTR/
ls -lhp ~/anaconda3/envs/TESTENV/lib/python3.7/site-packages/lusSTR/tests/

[rnmitchell]

Looks good. Thanks!