Cleaned up and extracted base functionality

Gianfranco,

Jesper and I cleaned up this script to work with:
- MacOS (e.g. mktemp /tmp/AWKPRACTICE_XXXXXXXX)
- run test from any directory
- run scenario_XX.bash from any directory
- use answer_XX.awk for each exercise
- tested on MacOS - GNU bash, version 3.2.51(1)-release (x86_64-apple-darwin13)
- tested on Windows7 Cygwin - GNU bash, version 4.1.10(4)-release (i686-pc-cygwin)
- tested on Linux RHEL 6.4 - GNU bash, version 4.1.2(1)-release (x86_64-redhat-linux-gnu)

Feel free to import changes and see if it runs.

Alternatively, you could clone my repo and test if runs on your environment.

Cheers!
n.