Update loops.step

Emphasizing the message about exponentiation breaks the `**` characters.
Update variables.step

Be clear that you need to run `irb` again after exiting it in the previous lesson.
Merge branch 'patch-4' of https://github.com/kejadlen/docs into kejadlen-patch-4
Merge branch 'patch-5' of https://github.com/kejadlen/docs into kejadlen-patch-5
Add gitattributes file to force line endings as LF
Renormalize line endings