Feature: get last Redmine response code

For debugging and logging ("Syntax error" is not clear reason)
Update Client.php
Merge pull request #50 from GuyFawkes/patch-1

Feature: get last Redmine response code
Merge pull request #51 from ascendro/auth

enabling regular login/password authentification
Merge pull request #52 from ascendro/customFields

Save users with custom fields attached
cs fixes + simplify Client::api() method
update readme
Merge remote-tracking branch 'remotes/creator/master'