Letters was causing issues with the colored gem and apparently is not supported
on 1.8.7.

This patch also removes the custom Pathname.glob based on Dir::glob.

Related #572 and #602.

Clean paths fix

This change is an update to an earlier pull request to fix Issue
https://github.com/CocoaPods/CocoaPods/pull/572.

Closes #550.

Closes #577.
Closes #575.

Closes #581.
Closes #569.

Add support for .hh header files

Need to support .hh files as headers to use the live555 rtp library.
Followed the pattern of this commit:

https://github.com/CocoaPods/CocoaPods/commit/f7587b16ffae55138df5a62949c2cc3ff2b98fae

That fixed issue #244 solving the same situation for .hpp headers.

The earlier fix for clean paths is forcing some directories to lower
case which could cause some side effects. This fix removes the
`File::FNM_CASEFOLD` flag from the call to `Dir.glob` and allows the
OS to treat the directories as they wish. This makes the paths
returned in the `clean_paths` method consistent with those returned in
the `expanded_paths` method.

Podfile & Lockfile error handling

Closes 568.

Closes #519
Closes #568

Closes #570