Adds a --file option that will either:

  - pull the date from a vimwiki filename
  - pull the date from a p1k3 entry path
  - pull the day from file's mtime

Aggregates some stuff by date range.

This is Tyler's bash version, just because it doesn't have much in the
way of dependencies.

firefox-wrapper: start firefox (a workaround for some $PATH nonsense).

edit-clipboard: open current contents of clipboard in $EDITOR, write them
back to clipboard.  relies on xclip.

mcd(): a function to make a path and cd into it.

These were missing a `%`.

This should be slightly more correct and doesn't result in an extra blank
line.

See: https://p1k3.com/2016/7/11/ - "extracting all (?) of the filenames
from packages available in debian"

Amends last commit by tacking on current changes.

I'd forgotten the specifics here.

The main thing here is that alt-[arrow] will work for jumping windows.

Does, for the moment, nothing.  Probably will never do anything.  But then
you never know.

Uses comm(1) and bash process substitution to show filenames common between
two directories.