Fix timezone offset adjustment where no RRULE.

Fixes issue where if data is provided in the VTIMEZONE block for both
standard and daylight saving offsets, but no RRULE is provided to switch
between them an error would be thrown.
Be more tolerant of new lines when parsing.

No longer throws errors when empty blank lines are added to the end of a
vcalendar string to parse.
Fix bug in timezone correction code.

Fixes error thrown when only STANDARD offset component of the VTIMEZONE
block is provided.
Merge pull request #11 from patrickmeiring/master