Add error checking to ViewProtobuf

There are protobufs that protoc can't parse.  When protoc --decode_raw
fails, it returns nothing to stdin, and writes "Failed to parse input."
to stderr. Before this commit, if protoc --decode_raw couldn't parse
the protobuf, the blank stdout output would get returned to the view;
with this commit stderr gets caught and returned to the view.
Merge pull request #118 from jasonanovak/protobufs

Add error checking to ViewProtobuf