Brewfile: Install `hashpump`
.bash_prompt: Speed up the Git commands for the prompt

Fixes #227 and closes #380.
.bash_profile: Enable tab completion for `git` and `g`

Closes #197.
Brewfile: add instructions on how to change the default shell to Bash 4
Brewfile: Install Node with npm

Ref. https://github.com/Homebrew/homebrew/pull/28075. Closes #362.
bootstrap.sh: Make `rsync` output numbers in a human-readable format

Closes #383.