Add default blank titles to year/month/day flydowns, and a flag to turn them on and off.

This also makes a bunch of methods protected instead of private. Will not break anything, and in theory will help us subclass if we ever need to.
WS and CS
prepare for release of 2.1.5
Update package version.
having a null  should still short-circuit the display, just not output a message
Add SwatString::getTimePeriodParts()

Breaks getHumanReadableTimePeriodParts() into two methods:
 * getTimePeriodParts() keeps all the logic of defining the $interval_parts you want returned, and calculating them.
 * getHumanReadableTimePeriodParts() is rewritten to use getTimePeriodParts() internally, but maintain old behaviour.

Using getTimePeriodParts() means you can keep the benefits over a straight DateInterval, without being forced to use getHumanReadableTimePeriodParts() strings.
Cleanup docs on getTimePeriodParts()
Cast days and weeks as int to match the other date parts returned.
Add weeks back to getHumanReadableTimePeriodParts() and fix days.

It was lost in the refactoring that added getTimePeriodParts().
Merge pull request #30 from isaacgrant/time-period-parts

Add SwatString::getTimePeriodParts()
Default to showing blank titles on the date part flydowns.
Merge pull request #28 from isaacgrant/date-entry-blank-titles

Add default blank titles to year/month/day flydowns
Don't display an empty conjunction.

Prevents two spaces from being displayed when the conjunction is null or
an empty string.
Merge pull request #32 from charleswaddell/hide-empty-conjunctions

Don't display an empty conjunction.
updated code standards
Merge pull request #31 from nburka/null-no-records-message

having an empty no_records_message should short-circuit the display, just not output a message
prepare for release of 2.1.6 | package party