Added option to specify flash policy server address/port and forceFlash,...

Don't be hasty, this is still open for discussion.
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* Gives user the option to specify flash socket policy address/port  and forceFlash (good for testing)
* Adds FlashSocket test case for FlashSockets

Related:
https://github.com/LearnBoost/engine.io-client/issues/232

TODO:
[ ] Assign test/support policy server port should not be fixed (SauseLabs fail)
[ ] Policy server port should be passed to test case (no fixed values)
[ ] Should use external module hashFlash to check support for flash like used in FlashSocket test case
[ ] Flash policy test case fails if it is not the first one in the file

Discussion:
* Should FlashSockets be an external plugin??