Refactor passing_functions_to_functions exercise based on Jesse's feedback
Rename to "introduction to callbacks"
Make letters and words more obvious what to do.
Cleanup
Explain !module.parent
Remove comments on bothArraysAreEqual the second time
Remove numeral prefixes for javascript files
Tie inline functions to anonymous functions
Begin extracting the command_line_arguments exercises
Extract the minimist instructions
Edit copy for readability, convention

s/javascript/JavaScript and do some minor sentence wrangling in
Intro to Callbacks README
Make stylistic edits to copy and code

Across all files in intro to callbacks section:

- End JS statements w/ semicolon
- Use double quotes, not single quotes, by default. Singles reserved for
  apostrophes and cases where a single-quoted string is expressly needed
- Nitpicky grammar and spelling edits
Make stylistic edits to copy and code in command-line args exercises

- Use double quotes by default
- s/javascript/JavaScript
- Minor copy, grammar, and spelling edits.
Merge pull request #9 from codeunion/refactor-to-incorporate-jesses-feedback

Refactor exercises based on Jesse's feedback