shell: increase cURL max-time to 5 mins

60 seconds is far too short; cURL was aborting downloads of binaries
that Homebrew was trying to install.
Install `bash` with Homebrew

Install the latest version of Bash.
Install packages to convert videos to gifs

Useful for turning screencasts of features or bugs into animated gifs
that can be embedded in READMEs or bug reports.