Slider.js corrections and additions

Source code and documentation are not matching in Slider.js. 

closes #1198, closes #1047, fixes #1095 , fixes #1073, fixes #252, fixes #1068 

#### Change 1:

On docs says:
>__initialStep__ - (number: defaults to 0) The step the slider will start at.

The default value in the source code was `-1`. 
This PR defaults to the `range` minimum, when set. 
Otherwise `0` as the documentation describes.

#### Change 2:

The `complete` event reads: *Fire when you're done dragging.* 
The `change` events reads *Fires when the Slider's value changes.*

As it is, these events are being fired (**[twice!](http://jsfiddle.net/tjBjF/)**) during initialize . 
This PR makes the initialize *silent*, not firing those events.

#### Change 3:
This PR also adds `move` event as suggested by @olvlvl. I think is useful since the existing `change` event is locked to the slider steps, which do not reflect the knob's drag position/movement. 

#### Change 4:
Imported a idea from @csuwildcat 's PR #253 to correct a bug described in #252

#### Change 5: 
As reported in #1073 modulus operator `%` can return unexpected results.
This PR addresses that and corrects a bug that  didn't allowed to have steps with decimals, ie only allowed integers.

Behavior before (`range [0, 5], steps 10` - decimal steps are ignored): http://jsfiddle.net/2vTqr/2/
Corrected behavior (decimal steps are not ignored):  http://jsfiddle.net/2vTqr/3/
Also, about modulus calculation: http://jsfiddle.net/HZWEf/1/

#### Change 6: 

Added Specs.
Specs with old code: http://jsfiddle.net/N4req/1/
Specs with code in this PR: http://jsfiddle.net/N4req/