.coafile: Integrate coala for code linting

[ashwini0529]

Closes https://github.com/manu-chroma/username-availability-checker/issues/26 Also fixes linting errors using coala

[manu-chroma]

@ashwini0529 can you checkout master and redo the linting fixes?

[manu-chroma]

We should add these bears as well:

[all.python]
language = Python
bears = QuotesBear
preferred_quotation = '
default_actions = *: ApplyPatchAction

[html]
files = templates/*.html
bears = HTMLLintBear
htmllint_ignore = optional

[yaml]
files = *.yml
bears = YAMLLintBear

[manu-chroma]

For this PR, we can just keep it to adding .coafile. There is a lot going on already.

We can introduce coala patches when no gci student is working on tasks and preferably in separate commits.

[manu-chroma]

ping @ashwini0529

[ashwini0529]

Just updating the PR 😄

[manu-chroma]

@ashwini0529 as mentioned before, please remove the coala patches from this PR. Also, you're having two commits. Please squash.

[ashwini0529]

@manu-chroma done 😄

[manu-chroma]

Thanks @ashwini0529