Refactor `FinalError::display_and_crash` into Error::Custom

`cd_into_same_dir_as`: allow the proper IO error to bubble up and add…

… docs

Release 0.1.5

Merge pull request ouch-org#20 from vrmiguel/dev

Update master from dev branch

Merge pull request ouch-org#9 from vrmiguel/bump-to-0.1.4

Bump to version 0.1.4