better error message if protoc is not installed, or errors from protoc #4
Description
(copied from mozy#6)
$ gem install ruby-protocol-buffers
$ ruby-protoc featureful.proto
HOME_PATH/.rvm/gems/ruby-1.8.7-p334/gems/ruby-protocol-buffers-1.0.1/lib/protocol_buffers/compiler.rb:16:in compile': 127 (ProtocolBuffers::CompileError) from HOME_PATH/.rvm/gems/ruby-1.8.7-p334/gems/ruby-protocol-buffers-1.0.1/bin/ruby-protoc:38 from HOME_PATH/.rvm/gems/ruby-1.8.7-p334/bin/ruby-protoc:19:inload'
from HOME_PATH/.rvm/gems/ruby-1.8.7-p334/bin/ruby-protoc:19
The featureful.proto file is taken straight from the current source code.