Revert short sha1 revision.

This deletion has been introduced on a previous PR.

Added changelog.

Fixed typo.
Merge pull request #1016 from blaugueux/patch-1

Revert short sha1 revision.
Improve the output of cap --help.

Remove options documentation for rake options that aren't applicable
to capistrano, briefly explain correct cap usage, and point users to
http://capistranorb.com.