Fix comment

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@172042 91177308-0d34-0410-b5e6-96231b3b80d8
Add .arcconfig for Arcanist support for Phabricator

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@172043 91177308-0d34-0410-b5e6-96231b3b80d8