tweak some code and alignment/visual issues
Merge branch 'master' of https://github.com/mikeweber/text-invoice

* 'master' of https://github.com/mikeweber/text-invoice:
  Made note of the samples in the example folder in the readme
  adding examples of yaml, html and pdf
  added install instructions
  Suggest using the 'case' statement to reduce cumbersome conditional evaluations