test-lessons.sh: Test mock-up lesson packaging with Bower

This shell script lets you test Bower-based packaging locally.  Note
that semver has stricter compatibility requirements for ^0.x [1]:

> ^0.1.3 := >=0.1.3-0 <0.2.0-0 "Compatible with 0.1.3". 0.x.x versions
> are special: the first non-zero component indicates potentially
> breaking changes, meaning the caret operator matches any version
> with the same first non-zero component starting at the specified
> version.

So of 0.1.0, 0.1.1, and 0.2.0, ^0.1 will match all but 0.2.0.  That
means the script currently wraps up with:

    workshop /tmp/z/workshop
    └─┬ git-lesson#0.1.0 extraneous
      └── shell-lesson#0.1.1 (latest is 0.2.0)

Next up here is working out a virtual dependency example.  I think we
can get this with Bower's renamed package format [2]:

    <name>=<package>#<version>

but I haven't added that to this test script yet.

[1]: https://github.com/isaacs/node-semver#ranges
[2]: http://bower.io/docs/api/#install