Update to work for Rails 4 + small edits

Quick review of sample app workflow plus some changes with how Rails 4 deals with the default `public/index.html` page.
Remove snarky commebt about IE
The colors Duke! The colors!

Highlight Ruby as Ruby in the README.
erb != Ruby
Clarify that they *should* create an account now.
Fix some typos.
Use rails generators to create controller.
Move the login/logout links closer to the end.
Prefer code over strings.
Specify that this is a terminal command.
Merge branch 'edits-cleanup' of github.com:nuclearsandwich/railsgirlsrdu into nuclearsandwich-edits-cleanup
Merge branch 'guide-changes' of github.com:nuclearsandwich/railsgirlsrdu into nuclearsandwich-guide-changes

Conflicts:
	README.md
Add emoji to readme
Add a section describing the emojicons.
Bumped back to rails 4
Formatting. How does it even?
Merge pull request #6 from nuclearsandwich/know-your-tools

Add a "Know your tools" section
Explain the Gemfile.