Fix a few typos in documentation

Add a Gitter chat badge to README.rst

Remove obsolete code

They haven't been used in a long time.

2.6 is unsupported. 2.6 is long unsupported.

Consistently spell the version checks that remain as PY2 or PY3 to make
them slightly easier to find.

Enable using coverage and coveralls for coverage reporting.

Set this up on travis.

This was just slightly tricky because of the use of 'j99' in the call to
bin/test.

Add a section on the pitfalls of __eq__/__hash__. Fixes #106.

The reader doesn't need to see the class that doesn't define eq and hash.

- Move doctest example into comment.
- Merge the (advanced) sections.
- Typos.

Noteworthy non-included storages: split base storages from others, NEO

Documentation on transactions and threading.

Conflicts:
	CHANGES.rst

Clear Connection.transaction_manager on close. Fixes #114

And other editorial changes.

More changes to come.