Corrected peterRiverColor hex code.

Hex code for peterRiverColor was the same as nephritisColor hex code.
Changed peterRiverColor to the correct one according to the web
http://flatuicolors.com.
Fix FUISwitch color issue in iOS 7.1

Issue:
Method was blending colors taking grayscale components first.
Fix:
Changed the order of the calls to convert the colors. First check if it
is possible to get the components in RGB. As last resort, go with
grayscale values.
Merge pull request #143 from davidcollado/master

Fix for FUISwitch color issue in iOS 7.1. Corrected peterRiverColor hex code.