Fix ImplicitDiv issues with dynamic ids after unclassed divs

[hackling]

Fixes #33

Credit to @parameme for his help with the regular expression solution

The ImplicitDiv linter has issues when an unclassed div has a preceding dynamic id.

The following examples will not report a lint, as I believe was the original intention of the linter.

%div{id: object.to_s}
%div[object.to_s]

I have confirmed that this change does not break any existing tests

Finished in 0.74166 seconds (files took 0.62902 seconds to load)
194 examples, 0 failures

[sds]

Thanks for the pull request, @hackling, and doubly so for writing tests.

Merged in 936fd8e.

[hackling]

@sds No problem. If you remember, can you please let me know when you bump the gem version, so I can update it and turn the ImplicitDiv linter on in our build server.