Use multi_json instead of json gem

closes #164
Update CHANGES
Merge pull request #165 from presidentbeef/update_rescanner2

Fix rescanner and add tests
Merge branch 'master' of github.com:presidentbeef/brakeman
Fix parentheses spacing warning
Bump to 1.8.2
Convert timestamp to string in JSON report
Add Symbol#to_s when using ok_json

this is so the multi_json gem will work with the
ok_json fallback
MultiJson.default_engine not MultiJson.engine
Do not process appending to HAML template variable

in the alias processor. Should fix #168
Update gemspec to latest ruby_parser stuff
Merge branch 'master' into simple_helper_scanning

Conflicts:
	test/apps/rails3.1/app/controllers/users_controller.rb
Add initial tests for FindReturnValue
Move helper method scanning to AliasProcessor
Basic tests for scanning simple helper methods
Add ability to pull ivars from any env

not just current
Track ivar assignment in helper methods
Fix expected warnings in tests
Remove old RubyParser code
Deal with RP3 getting rid of body Sexps