Revert "Removed v8::V8::Dispose call because it was causing SIGTRAPs in some exit scenarios. This is probably due to using the debug version of V8, but the documentation states that it's not necessary to call this anyway."

This reverts commit 0c011e8c3412b76514613af9326b9d0312837e3f.

Seems like for me, on v8 version 3.8.9.20, the opposite is true,
the test suite keeps failing at a rate of about 50%, if
V8::Dispose is not called.