Support for MatchCondition at DOMAnalyzer level

Currently MatchConditions were being set globaly at CSSFactory level.
But if we want to have multiple DOM Analyzers then this will fail. For
that reason added MatchCondition to Analyzer class.
refactored assignDom to call the newly defined method.
checking for null before registeringMatchCondition.
code refactoring

moved the check for matchCond and matching the selector in a function.
minor
private -> protected

made elementSelectorMatches protected in Analyzer as DirectAnalyzer was
duplicating the method.
update the JavaDocs
removed node type check

as the check was redundant, removed it.
Merge pull request #5 from UprootLabs/non-static-MatchCondition

Support for MatchCondition at DOMAnalyzer level