added link to github for contributors on the homepage
added twitter follow button to the bottom of talks page
Merge branch 'master' of https://github.com/mootpointer/rubyconf_miami_hub

Conflicts:
	source/index.slim
modified copy for contribution CTA on homepage
added modified ninefold sponsor message
edited contribute message on front page and twitter follow button. Header image responsive
Merge branch 'master' of https://github.com/mootpointer/rubyconf_miami_hub