Ensure Graph creates a copy of the x/yScale before modifying it

x/yScale is coming from the configuration dictionary which may be
referenced by the Graph creator, or shared with other Graphs. We need to
ensure we copy the scale so that our mutations do not change the object
given to us.
Allow empty data arrays in series.
Find correct domain even if the first series in stack is empty.

This can easily happen when series of different length are drawn and the RangeSlider is used to restrict the graph to a range where one of the series is empty.
Merge pull request #415 from dwt/support-empty-first-series-in-stack

Support empty first series in stack
Removed trailing comma in example
Merge pull request #420 from reustle/master

Removed trailing comma in example
provide a supported interface for toggling stacking
support resizing preview range sliders; closes #375; closes #417; closes #382
add x magnitude scale and improve barWidth calculation for bars renderer
use preview range slider in multi renderer example
refactor lineplot to work with multi renderer; closes #413; closes #414
Merge pull request #387 from dwt/clone-mutable-xscale

Ensure Graph creates a copy of the x/yScale before modifying it
update built libs
Update README.md
Add README.md note about $super and minification; closes #52
Only update graph once when toggling a series, not once per series.
Remove duplicate graph update in smoother.
Merge pull request #433 from msand/master

Optimize toggle and smoother performance.
Update copyright year

Fix outdated copyright year (update to 2014)
The copyright year was out of date. Copyright notices must reflect the current year. This commit updates the listed year to 2014.

see: http://www.copyright.gov/circs/circ01.pdf for more info
Merge pull request #446 from JoshSGman/update-copyright

Update copyright year