Changes from lein-protobuf

Forked to make it work with newer versions of other libraries

This is a stripped-down version of lein-protobuf. It behaves the same as lein-protobuf, with the following exceptions:

• It cannot download and compile the Google protocol buffer compiler for you. You must have protoc on your path.
• It can support multiple include directories. Specify these in your project as :protobuf-includes ["patha" "pathb" "pathc"]