Drop py34 target in tox.ini
Drop py34 target in tox.ini

We support py35 now.so it is no need to keep
the supoort for py34.

Change-Id: I18cb088116c038fe5255cedf7a6cab33d5e98e98

stackforge/solum-dashboard,stackforge/solum-dashboard,openstack/solum-dashboard,openstack/solum-dashboard