add 'e-clickable' to allow element with e-form to still be clickable

I needed to auto-focus on a x-editable element automatically (i.e. when adding a set of fields in a ng-repeat directive, I wanted one of them to already be ready to receive keystrokes).

I saw that there was a $editable property published to the directive scope, but there is no documentation of examples on how to actually use it. I would be very interested to hear your thoughts on this.

I'm asking for a pull request of a change that would allow someone who'd like to externally trigger an editable field to also be able to keep the click behavior by adding e-clickable to the field. Here's an example:

    <a editable-text="myTest" e-form="myField" e-clickable>{{myTest || 'Empty'}}</a>

I updated the docs but I didn't updated the tests because they were run on the docs page and I didn't want to just add a variation of the "Trigger Manually" section. If you'd like me to do so, let me know.

If you think I can achieve a similar result differently, please let me know. What I **really** need is simply to publish the editable-text's $show function to the parent controller.