Fixing version number

Mismatch between tagged version and specified version number. 
```shell
$ bower install
bower not-cached    https://github.com/isaacs/sax-js.git#*
bower resolve       https://github.com/isaacs/sax-js.git#*
bower checkout      sax#v0.6.0
bower deprecated    Package sax is using the deprecated component.json
bower mismatch      Version declared in the json (0.5.2) is different than the resolved one (0.6.0)
bower resolved      https://github.com/isaacs/sax-js.git#0.6.0
```