Merge pull request #30 from protobuf-ruby/feature/test/continuous-integration

Add Travis CI integration.
Update testing documentation and add build status.

Per working with @grobie, we decided to update the test process to use
the standard Rake-based workflow.  This commit updates the
documentation accordingly and adds continuous build status.
Merge pull request #31 from protobuf-ruby/feature/test/continuous-integration

Update testing documentation and add build status.
Support varint-encoded length-delimited buffers.

Official Google Protocol Buffers support varint-encoded
length-delimited message streams.

For comparison, see the following:

    1. AbstractMessageLite#writeDelimitedTo
    2. AbstractMessageLite#mergeDelimitedFrom
Code Review: Simplify delimited decoding.

This code review addresses @bernerdschaefer's comments about
simplifying the decoding process.