Added inviteEmail queryParam

@nicolashery PR ready for review.

@jh-bate the link should look like this http://localhost:3000/?inviteEmail=jamie.h.bategmail.com&inviteId=EzTwyF4jfYwTDtguHWXikn5PgQ01oKDj#/signup or http://localhost:3000/?inviteEmail=jamie.h.bategmail.com&inviteId=EzTwyF4jfYwTDtguHWXikn5PgQ01oKDj#/login

Notice the ? before #/login and #/signup