Fix MATLAB challenges numbering
Fix headers at regex lesson
More reformatting indentation
Added additional challenge to 04-cond to combine conditional, per discussion with @jdblischak
replaced parameter with argument, identified argument with a defualt value of TRUE, and changed name of argument to use_boxplot
Updated new challenge wording to drop boolean and instead refer to the use_boxplot argument
updated index.md
changed double to single quotes in 01-intro
changed single to double quotes in 02-reuse
Merge branch 'fix-string' of https://github.com/ashwinsrnth/bc into fix-string