readme: added information on how to generate the escape character

Make sure that users understand that on  different kayboard layouts you will have different ways of generating the escape character
Fix table formatting
Merge pull request #206 from vsekhar/patch-1

appc/spec: fix table formatting
readme: small changes to make the escape character generation look better

Changed it to proper code spans
Merge pull request #192 from virtualswede/master

readme: added information on how to generate the escape character
cas: use tmpdir for tests