Update handlers/notification/pushover.rb

I get this error if verify_mode is not set :

{"timestamp":"2013-01-23T14:34:21.393489+1000","message":"/usr/lib/ruby/1.8/net/http.rb:586:in `connect': SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B: certificate verify failed (OpenSSL::SSL::SSLError)","level":"info"}

so to get it to work for me I just commented out this line.

I don't know much about ruby and its http library, so maybe someone else can shed some light