Merge branch 'master' of https://github.com/kevinzhow/PNChart

Update pod

values of type 'NSInteger' should not be used as format arguments;

ShowLabel in default

Update readme

Fix warnnings

Merge pull request kevinzhow#175 from lunzii/master

Add options for chart legend font style.

* Improved Pie Chart and Legend Chart

Merge branch 'master' of github.com:kevinzhow/PNChart

Update Podspec