Add MIT license to Gemspec.
Remove Makefile and mkmf.log as they're generated by extconf.rb and mkmf.
Add bulletproofing around the management of config->rk and config->rkt kafka handles.

Avoid dereferencing or freeing null handles for Consumer and Producer classes.

JIRA: PART-3886
Turn off TRACE and DEBUG by default.

JIRA: PART-3886
Merge remote-tracking branch 'upstream/wip/PART-3886'

Conflicts:
	hermann.iml