Stuck. Installing Drush via Composer not working
Try adding the following to the end of your /Users/jensimmons/.bashrc file:

export PATH="$HOME/.composer/vendor/bin:$PATH"


and then run

source $HOME/.bashrc


Edit:

I just noticed there was a section in the Install/Update - Composer section of the Drush README.md file that mentions this:

https://github.com/drush-ops/drush#installupdate---composer

It's the second point "Make sure Composer's global bin directory is on the system PATH (recommended)"

Hope that helps.