Add speed button

[coraxyc]

Fixes #5

[coraxyc]

Leaving the Arrays import in MovementSystemTests; the speed change test uses the library to convert speed and direction keystrokes into a list

[CTrando]

Need to test with multiple entities, at the moment only one of them is sped up. Perhaps consider once finding an entity whose has an input component that says the key 'S' is pressed, loop through the other entities and update their move components if they have them.