Does not attempt to hit Internet when no connection available.

As part of the fix for #3, if there is no detected connected network, there's no point going through the rigmarole of making a web request and parsing JSON, which leads to two handled exceptions.
Adds empty view when no timetable data available
Adds loading indicator to list rows
Sets empty view to be hidden initially.

The empty view, even if you tell it to be GONE in XML, will initially be
set visible, because the list view is empty. Setting it in code to GONE
will prevent this behaviour from occurring until the first list items are
populated, or an error is triggered.
Merge pull request #11 from sh1989/networking

Networking