Additional Feature: Show only days in current month

setting ‘showOnlyCurrentMonth’ property in PMCalendarController to TRUE
will result in calendar hiding both days from other months and month
selection.
Resolved 'sizeWithFont' deprecation warnings

resolved sizeWithFont deprecation warnings when target is iOS 7.0
initialised CGSize' with CGSizeZero

initialised CGSize' with CGSizeZero
Added an NSAssert for dayFont
Merge pull request #36 from lukhns/master

Ability to show only the days in the current month, resolved deprecation warnings for iOS 7.0 target