Fix grammar issues in book's introduction
Merge pull request #78 from sodapopcan/book

Fix grammar issues in book's introduction
Use non-deprecated, secure HTTPS Rubygems source

Otherwise warning appears:

> The source :rubygems is deprecated because HTTP requests are insecure.
Test with Ruby 2.0.0 on Travis-CI
Merge pull request #80 from amarshall/test-ruby-2

Test with Ruby 2.0.0 on Travis-CI
Merge pull request #79 from amarshall/rubygems-source

Use non-deprecated, secure HTTPS Rubygems source
Fix a url in Learning section.
Merge pull request #82 from JuanitoFatas/master

Fix a url in Learning section.
Two characters saved in #require
Merge pull request #83 from somu/patch-1

Two characters saved in #require
improve summary and make it neutral
Merge pull request #85 from shime/patch-1

improve summary and make it neutral
Fix typo in description
Merge pull request #86 from gregkare/patch-1

Fix typo in description
fix grammar in documentation
Merge pull request #87 from shime/master

various grammar fixes