Adding exercises from the Software Carpentry 4.0 website
Moved exercises into subfolders of the corresponding topics
Ignore weird mac DS_Store files.
Merge pull request #48 from arokem/ignore_ds_store

Ignore weird mac DS_Store files.
Cleanup GitHub password section

1. Fix a typo in the title
2. Be explicit that the student is creating an account
Merge pull request #49 from ethanwhite/passwordtypo

Cleanup GitHub password section
Draft outline of testing section.
Outline of contents for testing cheat sheet.
Merge pull request #50 from benwaugh/master

Outline of testing section
Cheatsheet based on @LJWilliams's version (PR #30) with updates to match the Guide
Merge pull request #57 from pipitone/shell-cheatsheet

Cheatsheet based on @LJWilliams's version (PR #30) with updates to match the Guide
Merge pull request #34 from pipitone/swc_exercises

Exercises from the Software Carpentry 4.0 website