Find expansion

Updated the Applitools driver object so it mimics [the Selenium Ruby bindings Search Context more accurately](https://code.google.com/p/selenium/source/browse/rb/lib/selenium/webdriver/common/search_context.rb). Basically -- you should be able to find an element (or elements) by specifying locators either as a hash (e.g., `css: 'a'`) or as two arguments (e.g., `:css, 'a'`).

Not having this is trivial if people have good abstraction in their test code (e.g., [a facade layer](http://elementalselenium.com/tips/9-use-a-base-page-object)). But if they don't (which is more often than not), and if they're finding elements with a hash (which is fairly common), then the getting started Applitools experience will not be smooth (e.g., it will require a good amount of test rework).

Note: I also added an end-to-end test to verify that both approaches work for `find_element` and `find_elements`.