Port over managing dependencies (#19)

* Add common issues markdown from ember-cli.com
 - Addressing issue #3, item 10, "Port over Common Issues. Mostly copy and paste from this source code"
 - Converted the markdown file found here: https://raw.githubusercontent.com/ember-cli/ember-cli.github.io/master/_posts/2013-04-03-common-issues.md

* Update internal link to the Windows Support section

* Modify common-issues.md content per @sandstrom's suggestions
 - Clarify the heading for the npm packages section
 - Add a description for the Canary build section
 - Remove PhantomJS section
 - Fix the link to Vagrant to include https

* Remove references to PhantomJS in the Docker section
 - Commenting out Docker section until it can be rewritten without using PhantomJS

* Add managing dependancies markdown, taken from ember-cli.com
 - Addressing issue #3, "Port over managing dependencies."
 - Converted the markdown file found here: https://raw.githubusercontent.com/ember-cli/ember-cli.github.io/master/_posts/2013-04-08-managing-dependencies.md