Add an option to use single quotes for partials

[jeromedalbert]

Add a g:rails_single_quotes_style option. Addresses #458 and the discussions in #343.

I am not a Vimscript guru (being a recent Vim convert) but after hacking these lines together, this seems to work.

[tpope]

The basic logic for figuring out the diff line can be found in s:StageInfo(). I'd recommend duplicating it as a starting point. (Don't try to DRY it up.)

If a range is given, I'd say just use the first line of it, regardless of where the cursor is.

[lucasdf]

hey @odnoletkov , it seems you implemented something like this in your fork. Are you planning to integrate it into the plugin?

[odnoletkov]

See #37

[tpope]

Note the linked Fugitive PR is a prerequisite and the current bottleneck.