Replace static helper methods

#### Resolves #1240

**Changes:**
- All proxy method references have been moved to the bottom of Class.prototype extends for consistency. ie:
```js
_.extend(Marionette.Class.prototype, {
  // ... 
  triggerMethod: Marionette.triggerMethod,
  getOption: Marionette.proxyGetOption
});
```
- Classes always use their own helper methods instead of another Class'.* This is due to the way we currently write our tests (with spies rather than mock classes). ie:
```js
this.triggerMethod.call(foo, 'bar');
```
- Replaces all static helper method calls with proxy methods

--- 

*As I said before, I'm not a big fan of this, but it's the best I can do without breaking literally hundreds of tests