Issue #94: Protocol Buffers interface allows the creation of records with an empty key
Issue #94: return {error, msg} tuple instead of error atom for riakc_obj:new()
Issue #97: Update new to return {error, zero_length_key} and clean up unit tests
Issue #97: Consolidate construction of riakc_obj into build_client_obj/3
Issue #97: Use pattern matching on build_client_object instead of case statement
Issue #97: Replace try/catch test in invalid_key_test/0 with ?assertError/2
Merge branch 'bch-pbc-empty-key'