Refactor cli_server; add CLI server for Tornado

Now invoking ``cli_server`` should be similar to creating application;
just do ``cli_server('wsgi')`` or something like that. In other words,
the cli_server implementation is not CherryPy-only any more, and more
could be added later.
examples/hello: Update use of cli_server function

* Refactored view functions out of WSGI file
* Updated the invocation of ``cli_server``
examples: Update rest of cli_server invocations
Merge branch 'cli-server-refactor'