Add Travis CI integration.

This commit introduces nascent Travis CI integration for Beefcake,
which will make the triage of antique pull requests far easier and
more reliable.

Due to how antique some of the code and the tooling around it is, I
have opted to use a direct makefile (.travis.makefile) to drive the
tests instead of using Travis with its implicit environmental
assumption.
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.
Merge pull request #29 from matttproud/feature/coding/delimited-streams

Support varint-encoded length-delimited streams.
add test task to rakefile
helper to load test/unit
load helper in tests, set buffer_encode_test encoding
Update README for testing and Ruby 2.0.0 compat
Add definition step for generator

This allows messages to refer to themselves without needing to be smart
about inclusion order.
add more rubies to travis