Fix empty swagger descriptor

Move app.boot() before registration of loopback-explorer middleware,
because the swagger definition is built at the time of middleware
registration.
Mount REST API at `/api`

This change allows the Loopback REST adapter to own it's URL space
and consistently report 404 errors.

Additional benefits:
 - It should be easier to implement API versioning - different API
   versions can live at different sub-paths like '/api-v1'.
 - Application routes and static content will not clash with the URLs
   handled by the REST API.
test: Redirect stdout logs to stderr

Install beforeEach/afterEach hooks that setup redirection of all stdout
write()s to stderr for test runs. This way the log messages don't
corrupt the output of test reporters, especially in xunit xml format.
Merge pull request #20 from strongloop/feature/fix-swagger

Fix swagger; mount REST API at `/api`