data- attributes not picked up if changed

[gitbryan]

Using jquery 1.9.0

init of monthpicker checks to see if data has been set, but if the plugin has already been initialized it does not extend the element's data-start-year, data-final-year and data-selected-year attributes if they have changed.

Recommend cloning the element on re-init to get the updated attributes (since the first init causes jquery default .data() to lose its values) and reloading select.mtz-monthpicker-year.

[olleicua]

ignore #43
use #49