Sort warnings by fingerprint for more consistency between reports.

This sorting method leads to a more stable ordering of the JSON report.  This is useful when the JSON report is checked into version control.
Merge pull request #587 from jeffyip/sort_json_reports_by_fingerprint

Sort warnings by fingerprint for more consistency between reports.
Fix ERB parsing <%==

also update BLOCK_EXPR regex from head Rails
Merge pull request #589 from presidentbeef/fix_erb_parsing_double_equal

Fix ERB parsing <%==
Adds option "exit_on_new_warnings_only".  This is useful when using brakeman on a CI system that depends on the exit status to determine if new vulnerabilities have been detected and it is not desirable to have a non-zero exit status when vulnerabilities have been fixed.