Doc: Improve WQ Example Application

[dthain]

The current example WQ program (gzip some files) isn't an ideal example to show to new users. It's simple, which is good, but doesn't represent a typical use of WQ. And it has strange ergonomics in that the user must provide some extra files to compress.

Let's think of a better example application. It should have the following properties:

• High level program should be simple and straightforward (generate tasks, submit, and wait)
• Should involve a modest amount of I/O so that we can clearly demonstrate how to transfer/cache files.
• Application should have modest runtime (e.g. 5-10s) so that it's easy to show some parallel speedup on a small number of tasks.
• Should be self-contained so that the user doesn't have to download/install/configure anything additional.

Suggestions?

[dthain]

Some ideas:

• Task: An N-body simulation of the solar system + a comet at a particular location. App: parameter sweep of initial conditions. Pros: Easy to make this require an arbitrary amount of computation. Cons: Request some effort to understand/visualize the output.
• Task: Analyze one text in Project Gutenberg for word frequency, etc. App: Run in parallel across all Pros: Easy to understand inputs/outputs. Cons: Doesn't involve a huge amount of computation time.

[btovar]

We can do a brute-force algorithm for some known number, such as pi by probability:

https://mste.illinois.edu/activity/buffon/

Each task does the same thing, and then we collect everything in a final task.