Add bower configuration file

[Bower](http://bower.io/) is a package manager for the web. Estraverse is already [registered](http://sindresorhus.com/bower-components/). So it will be good to have escope registred too. For that we need:
* to have ```bower.json``` configuration file in the github repository (with estraverse dependency record) 
* install bower ```sudo npm -g bower```
* And register package ```bower register git@github.com:Constellation/escope.git``` 

It's possible to register package without ```bower.json``` file (like it was done for estraverse), but in this case we will lose dependency information.

[![Bower](https://si0.twimg.com/profile_images/3536632979/66db62603f426a8fc6664081811be6d4_normal.png)](http://bower.io/)