added a range feature

[pazams]

this PR introduces a feature that allows to specify both start and end values see live demo - http://plnkr.co/edit/bRJtRKGkSXJJm8O2lQwo?p=info

new api

radialObj.value([50,70]);  
radialObj.animate([10,95]); 

This does not break old api, it still works:

radialObj.value(5);  
radialObj.animate(60); 

It is now similar to the features in http://roundsliderui.com/ This PR suites my own needs, but it could be improved to handle both start and end display values, API callback values and more.

[s-yadav]

@pazams Its a nice addition, and as you said need to support displaying start and end value, and also touch interaction with start and end value. But for now, I can merge as older API will still work as before.

Your last pull request and this one caused conflict (This one does not have the precision fix) Can you fix the conflict and send PR again ?

[pazams]

@s-yadav, sure I can rebase and solve the conflict. But, maybe this is too early to get into master branch? We need to map how this feature will behave with current API, before coding:

• What should radialObj.value() return?
• What should onChange callback expect?
• How will mouse/touch behave?
• What values can initValue option take?

IMO, start a new branch 1.3.0-rc and I will rebase and issue the PR to that new branch. Then, we can work on more PR's till this feature will complete and ready for master branch. I have a lot on my hands right now, and I could help with this feature, but I can't guarantee I'll have time for all these issues. So let's work on this together?

[s-yadav]

Good point. I will start a new branch 1.4.0-rc. And sure we can work on this together.