Pandoc-source-exec

- Adding short captions.
- Adding capbelow option to place captions below the listing.

- Caption capabilities.
- More complete documentation.
- More examples.
- Added hidden feature pathlength to examples.

- Flat directory structure.
- Registration step for twine removed.
- REPLWrapper partly fixed.

- Fixing README links. Thanks pareyesv .

- Bugfix: when overwriting header-includes, pgfplots is now properly added and does not overwrite anymore.

- Adding `.hideimports` for Python to hide import statements.
- Adding `.hide` to hide the whole code.
- Adding `.plt [width=... height=...]` and `plt=width,height` to use matplotlib
plots as tikzimages.