Use 3 keys when testing KeysFile instead of 2

This will let us remove a middle key and make sure we don't leave blank
lines behind.
Use tap instead of temporary variable
Be explicit in tests which key we are deleting
Move common tests into shared example group
Remove line break as well when deleting keys
Merge branch 'chrishunt/dont-leave-blank-lines'

* chrishunt/dont-leave-blank-lines:
  Remove line break as well when deleting keys
  Move common tests into shared example group
  Be explicit in tests which key we are deleting
  Use tap instead of temporary variable
  Use 3 keys when testing KeysFile instead of 2
Bump version to 0.5.0