fix error in parsing a ISO8601-valid string 

Problem: "2014-07-02T18:01:00+0200" yields NaN

This is valid string according to [ISO8601](http://en.wikipedia.org/wiki/ISO_8601#Time_offsets_from_UTC). It also parses ok on the Chrome and Firefox default Javascript engines, but it fails on Safari OSX7.0.3 and IOS7.