Reduce 'character class has duplicated range' msgs

[ashmaroli]

This includes changes from #1177 and #1180. So, of now this is just a demonstration.
Once the above PRs are merged, the relevant changes of this PR will surface with a rebase.

[pyrmont]

@ashmaroli Thanks for making all these changes. They look good to me. The only ones I was a little curious about were the Elixir and Ruby changes that mashed open and closed together and then called squeeze on the result. Does the test suite go down this path, do you know?

[ashmaroli]

Does the test suite go down this path, do you know?

I'm guessing that the reason rake throws warnings there is most probably because those lines are invoked during the task..

[ashmaroli]

That said, I'd re-confirm against the visual test just to be sure before merging..

[pyrmont]

The Elixir visual sample doesn't appear to include any code that would test this but the Ruby lexer does. I don't see any regressions.