Allow to toggle recognizers via props.

[LinusBorg]

Idea for the syntax:

<v-touch 
  @swipe="callbackSwipe"
  "tap="callbackTap"

  <!-- enable all recognizers -->
  :enable="true"

  <!-- disable all recognizers-->
  :enable="false"

  <!-- Object Syntax: enable individual recognizers-->
  :enable="{swipe: true, tap: false}"
/>

TODO:

• add prop 'enabled', defaults tro true, accepts [Boolean, Object]
• Add Watcher that enables/disables recognizers according to that prop's value
• Update README
• add Tests

[LinusBorg]

Available in v2.0.0-beta.2