Corrected improper possessive apostrophe. Edited for concision.
Hyphenated modifiers.
Typo: '...code that *can* be mixed into other objects...'
Typo: '...look back at *a* previous example...'
Style: `yield()` instead of 'yield'
Typo: '...a more...' instead of '...amore...'
Typo: '...a few *different* possibilities...'
Typo: '...allows you to *execute* basic *nix file operations...'
Add second half of volume 4
Update index for v4
Merge branch 'master' of github.com:elm-city-craftworks/practicing-ruby-manuscripts
Add credit
Update README.md
Fixing a redundant entry in the Readme for v2 articles.
Merge pull request #1 from pradeepto/master

Fixing a redundant entry in the Readme for v2 articles.
Merge pull request #3 from gmcclure/master

Small punctuation changes.
Merge pull request #2 from d1/fix-typos

Fix typos
Update 011-domain-specific-api-construction.md
Update 012.1-tdd-lessons-learned-lesson-1.md
Update 012.2-tdd-lessons-learned-lesson-2.md