Update .gitignore so that the newly-added config.h is visible to git.
Update .gitignore so that the newly-added config.h is visible to git.

Change-Id: I0054c8d6f80fc71073ca70a121f1acafc12e030b

Livefyre/protobuf,google/protobuf,Livefyre/protobuf,Livefyre/protobuf,google/protobuf,google/protobuf,Livefyre/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,Livefyre/protobuf,google/protobuf,google/protobuf,google/protobuf