Fix collision with the glass

Because of some collision bug of Phaser, the player is able to cross the
glass when the drop is in the sunscreen state. In order to avoid that,
instead of using a line in Tiled to define the collision with the glass,
it is used a rectangle now.
Use hotkeys to make the drop jump

Using input.keyboard to jump makes the jump event happens several times.
This is not a problem for jumping now, but it will be when we change the
mechanic of the energy drop. Because of that, we replace the input.keyboard
by hotkeys. Using hotkeys, the action of jumping is detected only once,
that is what we want.
Refactor: remove not used code of handleKeyDown

Remove a not used code related with sliding in the diagonal straw.
Make the drop stay in energy state until jumping

Now the player uses the energy drop only when the drop jumps. This is
better because now the player has the option to use the energy drop
(make a higher jump) when he/she wants.
Enable the player to pause the game

Now the player is able to pause the game pressing Enter.

In order to implement this feature, we need to change how the timers of
the game are implemented. Instead of using the setTimeout function, we use
the Phaser.Timer class now. This change is needed because Phaser is not
able to pause and resume the timers when they are fired using setTimeout
function.