Fix escaping of JSON payload.

Use javax.json to create a JSON payload that escapes the content
that is sent to Jira.  This fixes 400 Bad request responses from
Jira whenever the test failure message has a double quote.

This also reformats the data sent to Jira so that it's formatted a bit
more nicely.
Merge pull request #2 from tipbit/fix-json-escaping

Fix escaping of JSON payload.