adding setTags +removing servername as test 

setTags allows to add a tags Object which will be serialized before the request is sent to Sentry,
and cleared after the request is sent.

the idea was simply not to break anything in the way captureMessage and captureException works,
but to allow to send more data to the Sentry Server.

also, there was a hardocded value of 'test' inside utils.getHostName().
server_name is a tag and should be optional, therefore i commented it out
at this point.