FIXED Crash when no internet

When an internet connection is required, the app now attempts to detect
whether there's an internet connection. If none is available, it will
display a toast for no internet, the string of which can be found and
modified in an updated strings.xml.

The issue was with Async.execute(), which crashes the app when no
internet connection is available. Alternatively, a try catch could be
used, though this would be potentially slower; may be worth evaluating
the speed of both methods during refactoring and maintenance, as this is
called somewhat often.