This makes it easier to run tests interactively and inspect the
results afterward, because the variables such as "el-get-sources" that
were set for the tests are still bound to the values they had during
the test.
This includes teaching methods that they now work with a symbolp PACKAGE,
some more cleaning up, and some load-path adjustments now that a part of the
code is in a subdirectory (methods).
Also include some of the tests used to convince oneself that the refactoring
didn't break any and all use cases for el-get, with some rough documentation
about how to use them.