Tell people not to be the BOFH.

This is a start to the "how not to be a sysadmin" section. I've tried to
achieve some balance between useful guidance and preaching.
Merged my changes into the existing crontab doc
Broke up long lines
Attempted to match line breaks from upstream
Adding my name to the contributions file
Updated credits/contributions doc link
Apparently github doesn't handle relative links in README files per https://github.com/github/markup/issues/101
Merge pull request #50 from handyman5/contributions_link

Reference to "credits" file is broken
Update shell_tools_101.rst

Added cut and sort to the list of commands that should be discussed.
Merge pull request #52 from jordandm/patch-1

Update shell_tools_101.rst
Update shell_tools_101.rst

Include df, du, find, and ls in the list of commands for working with your system.
Update meta/contributions.rst

Added self to list of contributors.
Update meta/contributions.rst

Added my email (jdm@dea-mattson.com).
Merge pull request #1 from jordandm/patch-1

Update shell_tools_101.rst commands included to include cut, df, du, find, ls, and sort
Update shell_tools_101.rst

Fix formatting for sort section.
Update shell_tools_101.rst

Fix sort formatting.
Update shell_tools_101.rst
Update shell_tools_101.rst

Fix command heading formatting.
adds initial content to databases_101, rough
Merge pull request #53 from jordandm/master

Added self to contributors; various fixes.