Init from the patch in the issue 3198
Formatting fixes
Add __init__.py for sympy/calculus
Add examples to docstring
Add references
Add tests
Autodetect funcs and vars
Test euler_equations interface
Get rid of using numbered_symbols, no integration here
Support lagrangians with higher-order derivatives
Test lagragians with high-order derivatives
Refine docstring
initial sphinx docs for calculus module
Bump version to 0.7.4.rc1
Add various empty __init__.py files to make setup.py happy
Fix PyPI uploading in the release fabfile

This is still untested, but I believe this will work.
Start work on using the GitHub releases API

Most code is copied from SymPy-bot. The release uploading is not implemented
yet.
Optionally save the GitHub token to a file
Make it more clear when mailmap_update has errors
Update .mailmap