Adds date path variables

Adds year, month, day, and date path variables.

Closes #6

LGTMs:
Jico

commit f2bd9ab7f6d04fcb591ad6739daf3e1df47629bf
Author: Chris Carey <chrisc@crowdtap.com>
Date:   Mon Jun 24 18:09:04 2013 -0400

    Removes double dagger in changelog

commit 09a8fd4e45b535cf34183ecc7295555e62834377
Author: Chris Carey <chrisc@crowdtap.com>
Date:   Mon Jun 24 18:05:11 2013 -0400

    Changes lpad param type and updates docs

commit 2b3a7319d144255365f241c0272d8d5807c8c4c9
Author: Chris Carey <chrisc@crowdtap.com>
Date:   Mon Jun 24 17:07:24 2013 -0400

    Extracts padding and updates test headers

commit feeac599ae46c0cf7cf5060485019e13623f550c
Author: Chris Carey <chrisc@crowdtap.com>
Date:   Mon Jun 24 15:55:10 2013 -0400

    Adds date variables