Improved Webconsole::Repl specs

Added valid token spec.

Fixed specs that were mocking methods or objects that weren't being used, such as $sandbox (was always nil), and Webconsole::Repl.token (method isn't ever called).

Extracted out common code into response_to and query helper methods.

Using let bindings and new contexts to further simplify the specs.
Captures stdout and stder, then sends it to the web console.

Inputs such as `puts "hello"`, `.ls` and many others now work as expected.
Loads user config, uses custom printer if one is available.