update Material to 2.2.0 and fix [FAKIcon allIcons]

[zhenian]

1. fix [FAKIcon allIcons] for all icon fonts

base on

/**
 *  Returns an dictionary of icons available for this icon font.
 *
 *  @return A dictionary of icons. The keys are character codes of icons, the corresponding value for a key is the name for that icon.
 */
+ (NSDictionary *)allIcons;

2. update Material Icons to version 2.2.0

change the CodeGenerator for Material basec on material codepoints

3. update FontAwesomeKitExample

add Material Icons to Icon Map

4. update FontAwesomeKit.podspec and README.md