add caveats about setwd() to 06-best_practices-R.Rmd
generate markdown file of Best Practices
Rewrote block so that it flows more nicely
knit a new version of 06-best_practices-R.md with Scott's edits
fix typo
rephrase to avoid the inaccurate use of the word 'crash'
remove bullet point about Windows vs Mac/Linux file paths
switch bullet point order and add note about using setwd() at the beginning of a script to avoid ending up in the wrong directory midway through
Merge pull request #658 from karawoo/teaching-10-r-setwd

Adding caveats about setwd() to R novice lesson