Add sprockets-helpers integration help to the readme

Ran into an issue from a prior configuration that was fairly confusing. Adding help to the readme.
Merge pull request #24 from plukevdh/patch-1

Add sprockets-helpers integration help to the readme
Don't encourage people to use this gem without a Gemfile
Add note on compiling assets on the fly in the development environment
Rewrite notes on installation
Make sure that we precompile the assets in the production environment
Use some different wording in the readme
Remove Gemfile.lock and add as ignored
Set https source
Add specs for custom behaviors
Fix typo with rake command
Merge pull request #26 from madwork/fix-compress-options

Fix compress options
Version bump
Minor grammar updates for README.md
Merge pull request #29 from pbevin/patch-1

Minor punctuation fixes for README.md
Remove erroneous comma from example setting
Merge pull request #30 from sobering/master

Remove erroneous comma from example setting
Remove .rb from Rake task require.

The .rb isn't necessary and will be automatically appended by Ruby.
Merge pull request #32 from benmanns/patch-1

Remove .rb from Rake task require.
Add Rakefile for running Rspec