Move mapping pre-conditions into a separate method #96
Start moving around logic in user mapping to make it easier to digest

refs #96
Pull WP user creation out of the mapping class #96
Fixing syntax errors and typos in user mapping #96
Allow mappings to be updated by member id or wp user id #96

We want to update by user id in most scenarios, but if a WP user is
already mapped to a Memberful member and we're changing the member
they're mapped to then we need to update by user id.
Fix references to Memberful_User_Map:: #96
Ensure $wp_user_existed_before_request is passed to the mapping logic #96
Merge pull request #97 from memberful/96-handle-connecting-to-different-site

96 handle connecting to different site