kiji-rest: REST-128. Allow extra tags in KijiREST/TSDB collector

 - Add flag: --tags="key=value,key=value"
 - Fix typo in KijiREST client

issue: https://jira.kiji.org/browse/REST-128
review: https://review.kiji.org/r/1880
commit: https://github.com/kijiproject/kiji-rest/commit/a9db0db1e2e263754a48b97a5df5f07430b4d78a