Reorganized the environments page to flow better.

- Added details about how to set the environment for an application
- Added details about setting the environment for Oil
- I updated the information regarding server environment variables as stevewest suggested. Let me know if this is still inaccurate. 

Signed-off-by: Zechariah Campbell
"there are two ways" then you say "the third", so there are three options? This might need some clarification.