Update Contributing doc & cleanup
Update Contributing doc & cleanup

Small changes to the Contributing documentation, and style cleanup

Change-Id: Idbfb913b225f40df45ffec0589721a79070dae9a
Closes-Bug: 1491469

takeshineshiro/horizon,NeCTAR-RC/horizon,dan1/horizon-x509,yeming233/horizon,saydulk/horizon,yeming233/horizon,django-leonardo/horizon,Dark-Hacker/horizon,BiznetGIO/horizon,Tesora/tesora-horizon,Tesora/tesora-horizon,noironetworks/horizon,NeCTAR-RC/horizon,noironetworks/horizon,bigswitch/horizon,damien-dg/horizon,davidcusatis/horizon,Dark-Hacker/horizon,ChameleonCloud/horizon,ChameleonCloud/horizon,bac/horizon,dan1/horizon-x509,redhat-openstack/horizon,FNST-OpenStack/horizon,Mirantis/mos-horizon,takeshineshiro/horizon,yeming233/horizon,saydulk/horizon,BiznetGIO/horizon,NeCTAR-RC/horizon,yeming233/horizon,anthonydillon/horizon,Mirantis/mos-horizon,django-leonardo/horizon,coreycb/horizon,Tesora/tesora-horizon,anthonydillon/horizon,BiznetGIO/horizon,Tesora/tesora-horizon,redhat-openstack/horizon,maestro-hybrid-cloud/horizon,damien-dg/horizon,bac/horizon,damien-dg/horizon,Dark-Hacker/horizon,coreycb/horizon,redhat-openstack/horizon,sandvine/horizon,maestro-hybrid-cloud/horizon,django-leonardo/horizon,sandvine/horizon,idjaw/horizon,dan1/horizon-x509,NeCTAR-RC/horizon,ChameleonCloud/horizon,FNST-OpenStack/horizon,philoniare/horizon,openstack/horizon,gerrive/horizon,openstack/horizon,idjaw/horizon,sandvine/horizon,bigswitch/horizon,saydulk/horizon,davidcusatis/horizon,damien-dg/horizon,takeshineshiro/horizon,noironetworks/horizon,redhat-cip/horizon,django-leonardo/horizon,davidcusatis/horizon,takeshineshiro/horizon,idjaw/horizon,redhat-cip/horizon,redhat-cip/horizon,anthonydillon/horizon,FNST-OpenStack/horizon,bigswitch/horizon,Dark-Hacker/horizon,wolverineav/horizon,bac/horizon,coreycb/horizon,coreycb/horizon,FNST-OpenStack/horizon,philoniare/horizon,wolverineav/horizon,redhat-cip/horizon,saydulk/horizon,dan1/horizon-x509,gerrive/horizon,openstack/horizon,redhat-openstack/horizon,maestro-hybrid-cloud/horizon,bac/horizon,bigswitch/horizon,maestro-hybrid-cloud/horizon,gerrive/horizon,ChameleonCloud/horizon,wolverineav/horizon,davidcusatis/horizon,BiznetGIO/horizon,gerrive/horizon,noironetworks/horizon,openstack/horizon,Mirantis/mos-horizon,wolverineav/horizon,sandvine/horizon,idjaw/horizon,philoniare/horizon,Mirantis/mos-horizon,anthonydillon/horizon,philoniare/horizon