Update contribute.html

Fixed typo s/gittup/gittip
Fixed rtd links

tldr; (s/http/https)

Updated readthedoc api javascript references to point to the secure domain api and documentation page since those don't run because of a security warning.
Merge pull request #206 from jefftriplett/patch-1

Updated contribute.html typo
Merge pull request #207 from jefftriplett/patch-2

Fixed rtd links
Merge branch 'master' into develop