Options parsing with commander + support for —clear-cache

Fixes #78 since commander automatically adds --version
0.0.6
Fixed typos in mv (promt -> prompt)
Merge pull request #80 from Delapouite/master

Fixed typos in mv (promt -> prompt)
Moved du back seperate pages for linux/osx because GNU has --max-depth, BSD has -d
Edited the examples to always explicitly specify unit as previous examples allowed return of block units which is probably not what your average user wants.
A bunch of new pages:
common/: dig, gzip, rm, sort, zfs, zpool
linux/: apt-get, shutdown
osx/: airport, caffeinate, diskutil, networksetup open, pgrep, qlmanage, say, shutdown, sysctl, system_profiler

Edits to existing pages:
curl: Added simple download example
find: Added iname and size exmaples
grep: Edited -c description
ps: Added wide lines example
ssh: edited -D description, added simple port forwarding example
unzip: added list option
Typos and missing trailing backticks galore.
Ignore emacs edited files
Added: Cal, srm, md5, md5sum, xed
Edited cp and rm. Fixed markdown escaping the wildcard.
Added cksum, touch, uname, which and sw_vers.
Ooops. Forgot a work.
Remove extraneous lookupd.md page
Removed two size examples.
Find.md sign switch.
Merge pull request #81 from notpeter/master

A bunch of new pages, split du back into osx/linux