Replace PyHamcrest with sure

It looks like a more BDD approach style
Add examples to README
Highlight python code in readme file
Use markdown instead of restructured text
Use the new readme.md file with setuptools
Add sure to requirements file
Merge branch 'sure-expectations'
Collapse multiple assertions for collection in one
Extract a formatters module and clean up cli one
Refactor towardscomposite (Runnable, Spec and Suite)
Execute specs in the same order than written and groups later
Implement before, after, before_all and after_all hooks
Use hook feature when testing mamba :)
Add another sample for spec loader
Add hooks to features
Add a predicate for checking if a spec was ended with an error
If an error was happened in execution exit with 1 error code
Add mamba to TravisCI
Use the same packages for installing with pip and distutils
Install travis packages with pip, and put mamba script with development mode