allow hook chaining (#125)

Author: gearsdigital

public/jquery.selectric.js

@@ -984,6 +984,8 @@
       }
 
       this[callbackName][hookName] = fn;
+
+      return this;
     },
 
     /**
@@ -992,6 +994,8 @@
      */
     remove: function(callbackName, hookName) {
       delete this[callbackName][hookName];
+
+      return this;
     }
   };