Monthpicker Style Updates

I updated the month picker with the following:

*  No more in-line styles of `padding: 5px` and `cursor: default` (replaced with this CSS)

 ```css
  td.ui-state-default.mtz-monthpicker-month {
    text-align: center; 
    cursor: pointer;
    padding: 5px;}
 ```
* Will default to a month instead of null if no month has been selected (you can pass the default month)
* When changing the year, the input field will also be udpated
* Added some in-line doc to help explain what's going on in the code
* Removed a lot of trailing whitespace
* Change setValue initial variable declaration so it doesn't keep referencing settings when it doesn't need to.
* Added the radix parameter to the parseInt calls so they are standards compliant
* Adding `mtz-monthpicker-month-selected` class to currently selected month
* Default the current selected month as selected
* Disable months when they are passed in as an argument

Here is the CSS I'm currently using to get styles for this:

```css
/* Styles added so monthpicker will look nice */
.ui-datepicker.ui-corner-all { -moz-border-radius: 4px; -webkit-border-radius: 4px; border-radius: 4px; }
.ui-widget-content .ui-state-default {background: url("../img/ui-bg_glass_75_e6e6e6_1x400.png") repeat-x scroll 50% 50% #E6E6E6; border: none; color: #555; font-weight: normal; outline: medium none;}
div.ui-datepicker {width: 17em; padding: .2em .2em 0;}
div.ui-datepicker-header.mtz-monthpicker {border: 1px solid #CCC; background-color: #E0E0E0; color: #fff; font-weight: bold;}
table.mtz-monthpicker {width: 100%; font-size: .9em; border-collapse: collapse; margin:0 0 .4em; }
td.ui-state-default.mtz-monthpicker-month {border: 1px solid #fff;}
td.ui-state-default.mtz-monthpicker-month {text-align: center; cursor: pointer; padding: 5px;}
td.ui-state-default.mtz-monthpicker-month:hover, td.ui-state-default.mtz-monthpicker-month-selected {background: none; background-color: #0F5895; color: #fff; cursor: pointer;}
td.ui-state-default.mtz-monthpicker-month:hover {background-color: #fff; color: #000;}
td.ui-state-disabled.mtz-monthpicker-month  {color: #E6E6E6;;}
td.ui-state-disabled.mtz-monthpicker-month:hover {background: url("../img/ui-bg_glass_75_e6e6e6_1x400.png") repeat-x scroll 50% 50% #E6E6E6; cursor: default; color:#E6E6E6;}
select.mtz-monthpicker-year {margin-top: 7px;}
```