WIP on documentation cleanup

This merges "documentation" and "guides", which
previously did not have clear semantic differences
WIP on documentation refactor
Fix syntax error in config.rb
Add more outline and write intro to guide section
some typo
revert filling -> filing
Merge pull request #156 from sly7-7/patch-1

fixed some typo
remember api visibility preference (#144)
added info about {{action}} and routers
Adds Handlebars basics guide
Add Core Concepts guide
Update handlebars basics to be less crazy
Add guide on prototype extensions
Clean up enumerables guide
added action.io to the list of ember users
Added Crowdstrike
Updated URL
Add nearzero.org to users.yml
Add Totango to WHO'S USING EMBER.JS?
More WIP on template guides