Block requests: add API

* pass request controller introduced in PhantomJS v1.9
* emit beforeSend event allowing modules to block given request by calling entry.block()

@see https://github.com/ariya/phantomjs/issues/10230
Add phantomas.getParam() to access command line parameters
Block domains: support --no-externals
blockDomains: add support for per domain filtering

Support --allow-domain and --block-domain
Update README
Require PhantomJS v1.9+

Need support for blocking requests

@see http://phantomjs.org/release-1.9.html
@see https://github.com/ariya/phantomjs/issues/10230
config.json.example: include "block-domain" param
Merge pull request #34 from macbre/issue-34-block-external-resources

Abort requests to external resources or given domains