Cleaned the shaking function
Cleaned the shaking function

the `shaking` flag is useless now that we can check it using the
remaining duration

TukekeSoft/melonJS,srbala/melonJS,melonjs/melonJS,gopalindians/melonJS,rlugojr/melonJS,MarkoIvanetic/melonJS,melonjs/melonJS,srbala/melonJS,MarkoIvanetic/melonJS,rlugojr/melonJS,TukekeSoft/melonJS,TukekeSoft/melonJS,srbala/melonJS,gopalindians/melonJS,rlugojr/melonJS,gopalindians/melonJS