Add setMemoryLimit & setTimeLimit setter methods
Refactor v8 call prologue/epilogue into function
Use prologues for V8Function calls, closes #129
Always push timer on stack to allow updates
Use std::deque for timer_stack

In order to update limits at runtime we need the stack to be iterable.
Allow to change & reset time limits
Allow to change & reset memory limits
Allow to impose memory & time limits
Add test showing that time limits can be prolonged
Remove set_memory_limit_002 test

The test is unfortunately unstable as it somehow depends on CPU speed.
v8 seems to precompute the result even so it hasn't reached the for
loop consuming the memory.

This can be proved easily by adding a sleep(1) call at the start of the
prolongTimeLimit function.  Then the memory limit is always tripped
even so v8 didn't have to do much until there
Make time limit tests pass more safely
Use isolate->RequestInterrupt to get heap size
Unwind stack after fatal error in V8Function, closes #130