Adds extension checking to plugin name resolution.  This closes issue #3.
Addresses the first three tasks in Issue #21. Button styling still needs to be addressed.
Adds CLI tests for starting a plugin with and without a file extension.
Refactors the Runner#set_pin method to order the pin state via pin.send(...)
Adds mDNS publishing and discovery.  This closes issue #29.
Updates Travis CI configuration to install necessary libraries before performing tests.
Removes insserv command from Travis CI configuration.
Refactors runner spec; raises the level of abstraction in button tests.
Adds links to other remote Pis to the web UI.  This addresses issue #8.