Merge pull request #2 from qapital/master

Implemented support for Selections MFA, some error handling
renamed development client factory to be more dichotomous
added ACH auth method to DefaultPlaidUserClient, refactored some internal stuff
fixed broken test due to changes
formatting for try/catch blocks
removed vestigial merge conflict code, added AccountNumbers object to Account object
Merge pull request #3 from Betterment/adam/master/add-ach-auth

Adam/master/add ach auth
Merge remote-tracking branch 'upstream/master'