Bug: Check for bzip2 in requirements.sh

[tensiondriven]

It appears that install_requirements.sh relies on bzip2, which is not installed on vanilla Ubuntu server by default:

Repro

1. Install ubuntu server headless
2. Git clone the repo
3. run ./install_requirements.sh

• Error:

tar (child): cannot run bzip2: No such file or directory
tar (child): trying lbzip2
tar (child): lbzip2: Cannot exec: No such file or directory
tar (child): Error is not recoverable: exiting now

To fix,

sudo apt-get install bzip2

The error that appears is fairly cryptic, and it isn't terribly easy to determine what happened since tar is relying on bzip2 as a dependency, but there's no reference to bzip2 in the install_requirements.sh script. If the installer checked for bzip2 before running, and failed with a nice message, it would help more novice users get on board faster.