Add .travis.yml for Travis CI

We want our tests to be run in Travis CI. This configuration file makes
that happen for Ruby 1.9.3, 2.0.0, and 2.1.0.

Change-Id: I3c35674466e3d03f76744cb791164718eb2323bb
Reviewed-on: http://gerrit.causes.com/37028
Reviewed-by: Shane da Silva <shane@causes.com>
Reviewed-by: Henric Trotzig <henric.trotzig@causes.com>
Tested-by: Joe Lencioni <joe.lencioni@causes.com>
Add gem version badge to readme

Change-Id: I2d2acaa25111568d7e4247ee4aa6ef8224fa601f
Reviewed-on: http://gerrit.causes.com/37029
Reviewed-by: Shane da Silva <shane@causes.com>
Reviewed-by: Henric Trotzig <henric.trotzig@causes.com>
Tested-by: Joe Lencioni <joe.lencioni@causes.com>