FEATURE: Indicate results by exit code
FEATURE: Indicate results by exit code

Introduce new command line option '-e'/'--exitcode' which will
make client produce non-zero exit code if any of printed plugins
has ERROR or WARN result.

Signed-off-by: Petr Benas <b6540373b5ff919b9c46e2f09e2ceb1f921dcaee@gooddata.com>

gooddata/smoker,gooddata/smoker