2.6.0: Tabular dates and ordinal suffixes

Added

• Adds two new date methods — apmonthtab and apdatetab. These two are identical to apmonth and apdate except months are output in AP's tabular format instead. Instead of Sept. you get Sep, etc.
• The logic for determining the correct suffix in ordinal has been extracted and made into its own method called ordinalsuffix. This makes it possible to access the correct suffix for a number without modifying the original value. Great for if you'd like to style the number and suffix differently, or just want to output them separately. Credit to @sawyerclick for the suggestion in #283!