add documentation for mocking HasStrictTraits methods
minor corrections
fix spelling
add `documentation` command into setup.py to simplify building the
documentation
rework the testing section documentation
minor rework
fix typo
rework paragraph
pep8 on changes
move long comment above the line.
rewokr the text
Merge pull request #133 from enthought/update-testing-documentation

Update the testing section of the documentation