Minor changes in README.md.
Improve VM building message.
Add name and license to script.
Add proper exit codes to commands.
Only determine & export DOCKER_HOST when dosx_start is called.
Minor syntax improvements.
Change she-bang from /bin/sh to /bin/bash.

Also add -e flag to echo commands.
This change is needed for the echo -n (no trailing newline) flag,
which will be used by upcoming features.
Add red color to install error messages.
Add warning and confirmation to updating or installing Python/Pip.
Add dependency names to installation error messages.