Permuta

Fixed
- Allow for a mix of permutation and mesh patterns in MeshBasis

Added
- The `occurences_in` method of permutation can can handle coloured
permutations.
- Support for containment of mesh pattern in a mesh pattern.

Added
- The ascii_plot, and to_tikz method in MeshPatt
- is_subclass method in Av
- Support for avoidance of mesh patterns with `Av`
Removed
- The broken latex method in MeshPatt
Fixed
- Wrong examples in the README. README.rst is now tested

Added
- Made master branch deploy to PyPi.
- Added testing for Python 3.7 and 3.8.
- Added a from integer method, for creating a Perm from integer.
- Added inversions and non-inversions function that yield pairs.
Changed
- Updated repr and str methods to Av, PermSetAll and PermSetStatic.
- The string of a Perm is now one-line notation.
- Can no longer initialise Perm with an integer.
Removed
- The demo.
- Broken plot function
- Support for Python 3.4 and earlier.
Fixed
- The ascii plot, and to_tikz method in Perm.
- Bug in polynomial checker.

Added
- Readme was rewritten in ReST.
- Classifiers and python versions added to setup.py.

Added
- This CHANGELOG file.
- Package added to PYPI
- Tests passing.
- Conforming to PEP8.