Improves mobile dropkick + performance boost

• ADDITION : DK now reverts to the orginal selects on mobile while
still maintaining styled ".dk_toogle"
• ADDITION : Ability to force dropkick normal mobile through setting {
nativeMobile : false }
• IMPROVES : performance through chaining some operations
• IMPROVES : reset method
• FIX : setValue method now assesses the existence of the option in the
<select> before applying
• CLEAN : reload/refresh duplicated methods, now is just refresh
• CLEAN : things unused and redundant
Linted the code
Changed the comments at the top of the file
Fixes theme and refresh methods + progressive enhancement

- Fixes the theme and refresh methods to work both if <select> or
dk_container are called
-  Bring back filter gradients for themes in IE < 8
Updating readme for version 1.3 changes
Merge pull request #147 from Robdel12/version-1.3

Merging in Version 1.3