Improve dependencies definition

[Sinclert]

Before starting with the pyhf schema integration, I think it is better if dependencies are defined in a single place (setup.py) instead of being define both in requirements.txt and setup.py.

The reason to move them to setup.py is because this tool lays into the "package" category, not in the "application" one.

In addition, I have:

• Bumped up version to 0.2.2.
• Added license header to .travis.yml.
• Removed duplication of installation within travis.yml.
• Formatted setup.py.

[alisonrclarke]

Looks good to me. @GraemeWatt your call on the version number - I guess if we don't normally bump it until we do the release then perhaps we should follow that process?

[GraemeWatt]

I've left the version number at 0.2.2. I don't think it matters too much, but it's probably better to increase it after making a tagged release. (In the past, I didn't fully understand the GitHub integration with PyPI and I was worried that bumping the version number might trigger a release automatically.)