Remove unused json imports; move json imports to utility

Fixes #7
upgrade tornado to 4.0.2
import backports.ssl_match_hostname 3.4.0.2
override to enable support for allowing alternate origins

To accept all cross-origin traffic (which was the default prior to Tornado 4.0), simply override this method to always return true.
Merge pull request #126 from Rayman/develop

upgrade tornado to 4.0.2
Removes EOL Groovy from Travis build.
Removes missed groovy source.
Merge pull request #125 from megawac/json

Remove unused imports; move json imports to utility
changelog updated
0.6.2
Merge branch 'develop' of github.com:RobotWebTools/rosbridge_suite