Ignore files related to Cocoapods.

These include Podfile, Podfile.lock, and Pods/.
Only ignore Pods/ for CocoaPods.
Ignore everything in the Pods directory.
Reverting https://github.com/github/linguist/pull/1268
Samples
Merge pull request #1352 from github/assembly-inc-revert

Reverting https://github.com/github/linguist/pull/1268
Testing Pods
Merge pull request #1353 from github/1217-local

1217 local