Added more tests for nested tag retrieval
Added the content filter

It will return whatever is inside the body of the elements filtered out. It will also return any html
elements nested within an html element.
Added extra test for Combination
Reimplemented the Combination filter to use flatMap.
Added implementation of HtmlProcessor constructor from a File.

Also removed dependency of `util-html` on `util-io`.

Also removed the "scala-check" and "specs2" from the sbt build path because they required
the usage of the -Yrangepos flag which makes the compiler bug when compiling some tests.
Since those where there "just in case" there is no adverse consequence to removing them.