Add weapon toggle inputs to InputManager.

New inputmanager methods:
TogglePrimary: check if Q was tapped
ToggleSecondary: check if E was tapped
NumKey: return int corresponding to pressed numkey, or -1 if none pressed
Spawn unicorns on left and right screen sides
Change unicorn sprite angling
Work on unicorn movement
Improve unicorn behavior.

Unicorns now spawn on horizontal level edges, scan vertically for the
player, and charge horizontally. They can now also be eaten by a black
hole.
Merge branch 'improved-unicorn'
Merge pull request #31 from murphyslaw480/weapon-select-input

Add weapon toggle inputs to InputManager.
Merge pull request #32 from murphyslaw480/improved-unicorn

Improved unicorn
Re-Vamped weapon manager to inventory manager

I changed weaponmanger to inventory manager. I added an item.cs file
because that is the object I am using in inventory manager.

It is probably this will change but it takes out the weapon switching
making room for item switching/getting.

Let me know if there are problems.
Merge pull request #34 from kalgynirae/andrew-branch900000000

Re-Vamped weapon manager to inventory manager
Add logo graphic to the README
Clarify git instructions in the README
Add new art assets.

Add new goblin and unicorn art.
Merge pull request #36 from murphyslaw480/master

Art update
Added basic GUI to screen
Merge remote-tracking branch 'origin/master' into guibranch

Conflicts:
	SpaceGame/SpaceGame/states/Level.cs
Added Health Bar functionality
Added functionality for void bar