firebase-ios-sdk

Allow clang-format to find Firestore/Source/Auth (#508)

* Avoid pruning paths with find

find . -path foo -path bar -path baz is horrifically inefficient;
properly excluding all of FirebaseAuth without excluding
Firestore/Source/Auth ends up taking 1.5 minutes on my machine.

Deleting via sed is much faster.

* Allow a branch name or filenames to be specified on the command line

e.g. ./scripts/style.sh master formats only files changed since master.

* Format Firebase/Source/Auth code

* Use alternate delimeter for path regexen