starting to refactor CrawlElement
fixing a few compile errors in CandidateElementExtractor
Removed unused imports and unused variables from CandidateElementExtractor.java and CrawlElement.java
fixing typo of comment in CrawlAttribute
deleted asCrawlElements
deleted unneeded files and classes
Recreated CrawAttributeTest to test match method
Merge remote-tracking branch 'origin/pr/196'

Conflicts:
	core/src/main/java/com/crawljax/core/CandidateElementExtractor.java
	core/src/main/java/com/crawljax/core/configuration/CrawlAttribute.java