Allow crawljax to visit external urls specified by alsoCrawl(String url) - Issue #93

Our team, Lab B1, the original team inquiring about issue #93, upon observing a rejected fail request on the same issue, has renewed our code.

How we understand is that currently Crawljax only visits links within the domain of the seed url. 

This update adds a new method, alsoCrawl(String url), within CrawljaxConfigurationBuilder
that gives Crawljax the ability to visit specified external urls.

For example, specifying builder.alsoCrawl("news.google.com"), will allow Crawljax to click any link to new.google.com.