Fix Travis Test for Ruby 1.8.7
Fix Travis Test for Ruby 1.8.7

Use an earlier version of the `hashdiff` gem (0.3.5) to avoid a use of the
Ruby 1.9 hash syntax in the newer version of `hashdiff`.

See [hashdiff issue 38](https://github.com/liufengyun/hashdiff/issues/38)

sendsonar/send_sonar_gem