added svg translate helper
add rotate and transform helpers
added initial histogram
render empty histogram
added data loading for histogram
added bin redrawing
created svg and bin group
added selection change event
renamed histogram load function to bin
added x-axis to histogram
update karma dependency

	modified:   package.json
refactor histogram interface

The previous interface maintained the state of the DOM element, input
data and plot specific state. The new interface allows multiple datasets
to be binned and exchanged.

	modified:   specs/histogram_spec.js
	modified:   src/histogram.js
add default styles for histogram

	new file:   css/histogram.css
add css minification to distribution

* Add files config to consolidate file patterns
* Add grunt-contrib-css-min dependency

	modified:   Gruntfile.js
fix bars being draw incorrectly

Remove typo that cause the bar width to be incorrectly calculated.

	modified:   src/histogram.js
fix histogram updating and bar selection

The histogram supports multiple histogram instances which may contain
different configuration settings.

* Fix histogram sizing after the configuration has changed.
* Update the axis when drawing new bins
* Fix the bar selection to select the correct bins.
* Rename `config.color` to colors to specify that this allows an array
  of colors.

	modified:   specs/histogram_spec.js
	modified:   src/histogram.js
add optional accessor function argument for bin

Allow complex data to be binned by passing an accessor function to bin.

	modified:   src/histogram.js
add histogram to the bioplot module namespace.

	modified:   src/histogram.js
add setter methods and minor class tweak

	modified:   src/histogram.js
update d3 version dependency

	modified:   bower.json