Add package manager support.

## Package Managers

- npm
- bower
- volo

## Summary of Changes

- generate `strophe.js` for browser.
- unignore `strophe.js`.
- add bower.json
- add `volo` object to `pacakge.json`
- include only essential `files` for `npm install`

## End Result

	% npm install strophejs
	% volo add strophejs
	% bower install strophejs
	% tree
    
![](https://cloudup.com/cKT9ucahX-h+)