Remove single quotes from DuplicateProperty output

- By using ' in the linter, the XML formatter will produce invalid XML,
  since single-quotes are used for strings in the XML
- Replacing the single-quote with ` fixes this issue and ensures valid XML
  output

Change-Id: If5691a5b680e274cbc319d06ae90f88037821f1a
Reviewed-on: http://gerrit.causes.com/36031
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>
Add Ruby 2.1.0 testing in TravisCI

We've technically supported this for a while, but let's make it
official.

Change-Id: Iee4191deca9b2677d5116374581f63cd53a32ec5
Reviewed-on: http://gerrit.causes.com/36032
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>