Accept also ':' as key/value delimiter

The `:` is used frequently in Python .ini files parsed by ConfigParser.

> "The configuration file consists of sections, led by a [section] header and followed by name: value entries, with continuations in the style of RFC 822 (see section 3.1.1, “LONG HEADER FIELDS”); name=value is also accepted."

See [ConfigParser](http://docs.python.org/2/library/configparser.html) for more information.