Update matchit support

Hi, here are some updates that I hope are useful for the project. This repo is the first one that shows up in the google search for `vim handlebars` so I think it makes sense to keep it up to date - at least thinking about the users of this plugin that should have the best support for the given filetype.

All updates are taken from [this repo](https://github.com/juvenn/mustache.vim) where I submitted a few of these changes too.

Here are the improvements:
 - remove indent file (it is not necessary now since html file type is used)
 - source handlebars plugin file
 - support for `matchit.vim` % command

With matchit support, pressing `%` when cursor is on any of the `#if isActive` chars will jump to `else`. Pressing `%` again will make a jump to `/if`, then `#if ...` again etc.
```
{{#if isActive}}
  <img src="star.gif" alt="Active">
{{else}}
  <img src="cry.gif" alt="Inactive">
{{/if}}
```

Let me know what do you think of the changes? Feel free give suggestion!