Time support plugin

WIP :construction: 

This PR:

* adds the ability to register plugins with the date range picker - using the same basic plugin architecture from the Tabler codebase.
* adds a time support plugin which when enabled renders a panel within the date range picker and allows the user to specify a time for each calendar

![timepicker](https://cloud.githubusercontent.com/assets/1387956/4456668/1c28e22c-488d-11e4-9a0c-33f2a212be59.gif)

:+1: wasn't a fan of this function/approach really so split it into two separate functions.
```
        updateStartTime: function(time) {
            this.startPanel.setTime(time.format('HH:mm'));
        },

        updateEndTime: function(time) {
            this.endPanel.setTime(time.format('HH:mm'));
        },

```