2nd g transform fix

[taras]

• [x] Upgraded ember-cli-d3-shape to fix svgs parsing problem in Safari
• [x] Added x axis repositioning to element creation instead of after transition
• [x] Added arc tween to pie chart to fix errors that it was throwing on resize
• [x] Added throttling to buttons in the demo app
• [x] Upgraded to ember-reactive-helpers 0.3.7
• [x] Upgrade version of ember-d3-helpers when https://github.com/LocusEnergy/ember-d3-helpers/pull/11 is merged
• [x] fixes interpolate-helper dependency (closes https://github.com/LocusEnergy/ember-sparkles/issues/20)

[ghost]

throttling the toggle data buttons is a clever, reasonable fix for our transition error for now - I think we can implement something similar in our production app that is using this library.