Make the code in the FX module simpler

Make the code in the FX module simpler

Here are the changes that have been made:
  - The loop counter is now incrementing (from 0 to loops)
  - The loop counter increment even when loops is true
  - Add absPos, the absolute position of an animation which is its position in
 the context of its complete duration (including delay and loops)
  - Make the methods speed, pause/resume affect the delay
  - The method step no longer needs to recalculate the value of situation.start
  - Add a second parameter to the method at to allow it to receive an absolute
  position
  - Fix the bug where the method at invert the passed position while the
  animation is running backward

Also, I modified the tests of the FX module that required timing to use
Jasmine Clock, so now it takes less than 1 second to run all the tests!