Feature/dependency injection

[iampeterbanjo]

addresses #31

[SimonWaldherr]

thanks for your pr, can you please add your example to the readme file.
what should go Shellrun do??

[iampeterbanjo]

thanks - i've updated the reame.

[SimonWaldherr]

Please think about whether you want to consider a rebase to cleanup the commit history: https://git-scm.com/book/en/v2/Git-Tools-Rewriting-History

[iampeterbanjo]

thanks. i rebased it