Expand on injective functions.
Merge branch 'develop' of github.com:learnmath/lysa into develop
Have Travis bot only tell us if a build status changes.
Add subset content.
Merge pull request #83 from wei2912/travis-bot-shut-up

Get the Travis bot to shut up about useless messages
Merge pull request #84 from jesyspa/develop

Wrote sections on injective functions and subsets