Integrating JSErrorCollector for firefox
Included testcase: no error is thrown when no javascripterror on page
Merge branch 'master' of https://github.com/johw12/thucydides

Conflicts:
	thucydides-junit/src/test/java/net/thucydides/samples/SampleJavascriptErrorFound.java
added testcase: check if no error if no javascripterror on page