New models

Oxygen, Hydrogen, CO2, Methanal
Added HUD mission message
Hud Message displays for first 10 sec only of gameplay.
Objective message is displayed for first 5 seconds and then 5 seconds after hitting the h key.
Merge pull request #14 from themolecularmoose/user-story-21

User story 21
Added a bunch of collectables

also fixed methane (needed to update main scene to), made collectables
asset folder
forgot to add this oxygen prefab update
Added 3 spinning obstacles.
Added lighting
Obstacles are now bright pink, long, and thin. There are also more of them.
committing meta files
Merge pull request #16 from themolecularmoose/US13-Adding-Obsticles

Us13 adding obsticles
Merge remote-tracking branch 'origin/master' into user_story_15

Conflicts:
	unity-project/Assets/Scenes/main_game.unity
from master
Merge pull request #15 from themolecularmoose/user_story_15

User story 15
Fixing merge conflict and merging with master