JCStockGraph can support iOS6.0

[derjohng]

It can works under iOS6 after I modified the file "JCStockGraph.podspec"
s.platform = :ios, '6.0'
s.ios.deployment_target = '6.0'

Suggest change from 7.0 to 6.0, and more projects can use this repository. ^^

[jconst]

I've changed the podspec. I'll push a new version to cocoapods once we take care of your other issue.