DuckPAN Help and pod2usage Improvements

//cc @killerfish @mwmiller 

This builds on #169, I've heavily reformatted the POD based on proper POD syntax. Now it's super ugly and hard to read :smiley: , but it looks much better imo when DuckPAN spits it out.

The biggest change is that `duckpan` will only print out the SYNOPSIS section of the POD which I've made to look similar to the output from running `git`.

Meanwhile, `duckpan help` or `man duckpan` will print out the full contents of the POD.

If we really want, we can have `duckpan help` only output SYNOPSIS, OPTIONS and ARGUMENTS if they're filled out properly and have the man page spit out everything (like the SEE ALSO, CONTRIBUTION, SUPPORT).

Not sure if I care enough for those though...