Adding a global switch that will check for global header imports

[jeffctown]

I work daily on an iOS App that has multiple frameworks that live in the same repository and are used by my app. When I use fui on my repo, I end up getting a lot of false positives that tell me that my frameworks have unused imports when they are actually used. The reason the references are not found is because these framework classes are imported as global imports (#import <Framework/Class.h>).

This PR is to add a -g or --global switch to perform a regex against imports in this format. Adding a regex does decrease performance time, so I thought it made sense to have this switch default to false to not affect computation time for users who do not need this functionality.

Here are computation times for my project (it's a pretty big project, 500k+ lines).

Global Switch Disabled
real 3m38.529s
user 2m17.454s
sys 1m20.829s

Global Switch Enabled
real 5m20.673s
user 3m53.501s
sys 1m26.923s

Unit tests are included.

FYI - I've never contributed to a ruby project before, so please don't hesitate to tell me if there are obvious improvements that can be made to this pull request (thank you Rubocop!).

[dblock]

Looks good with a few changes, thinking out loud ...

I think if we are going to have switches, we should have both --global-imports and --local-imports, and I would not worry about performance and default both to true. To be consistent since we already have a x option that ignores something maybe we should have --ignoreglobal and --ignorelocal or if we want to make it prettier, --ignore-xib-files, --ignore-global-imports, --ignore-local-imports to skip? I think I would prefer a backwards incompatible change and do the latter because it's prettier.

The README needs an update too.

[jeffctown]

@dblock - I agree with the "prettier" switches that you described above, so I updated them to be --ignore-xib-files, --ignore-global-imports, and --ignore-local-imports. I also turned on the global checks by default.

[jeffctown]

README updated.

[dblock]

Merged. Thank you.

Want to help me comaintain this thing @jeffctown? Maybe make the next release? Drop me an email to dblock at dblock dot org if you're interested with your rubygems username.