Typos

[jmandel]

Reported by Joseph Lorenzo Hall via http://wiki.siframework.org/BlueButtonPlus+Pull+API+Documentation+Consensus

• In "4. App exchanges authorization code for access token" there is a typo: "REQIRED": http://blue-button.github.io/blue-button-plus-pull/#authorization-code
• In "Using the BB+ Clinical API" there are two typos: "endpoing" and "or ay valid": http://blue-button.github.io/blue-button-plus-pull/#clinical-api
• In Push Authorization -> User Authorization Flow there is a typo: "provider to send updates them updates": http://blue-button.github.io/blue-button-plus-pull/#push-authorization
• A little farther down, in "Verify authorization results" there is a typo: "aubbthorized"