Additional examples/tests

[jonathancallahan]

We need to have examples (at least in local_examples/) that demonstrate how to use beakr as a replacement for jug in our existing web services. By far the most common use case is to attach functions to URL paths. The functions will typically:

• accept req, res, err
• extract parameters from a browser initiated GET request
• if not already found in a cache directory: 1) run a bunch of R code; and 2) write a file to disk
• read a file from disk
• return one of: 1) a blob of json with the file URL; or 2) the file itself

File types that we currently serve include:

• json
• text
• csv
• pdf
• png
• html

But we want to be able to serve up just about anything along with the proper mime type. (See the mime package.)

[hmrtn]

demonstrated in test_Repeater_beakr.R.