Use latest (v2.37) version of Selenium in Travis build

1. update Selenium version, used in build
2. tune (remove old and add new) versions of DomCrawler used in Travis build matrix
3. changing drag-n-drop implementation to basic mouse down/move/up stuff (as in Selenium2) for better compatibility
Merge pull request #19 from aik099/use-latest-selenium-in-tests-feat

Use latest (v2.37) version of Selenium in Travis build