add python 3.7 to the testmatrix
add python 3.7 to the testmatrix

voxpupuli/puppetboard,johnzimm/puppetboard,johnzimm/puppetboard,grandich/puppetboard,voxpupuli/puppetboard,grandich/puppetboard,johnzimm/xx-puppetboard,grandich/puppetboard,voxpupuli/puppetboard,johnzimm/xx-puppetboard,puppet-community/puppetboard,johnzimm/xx-puppetboard,puppet-community/puppetboard,grandich/puppetboard,johnzimm/puppetboard,puppet-community/puppetboard,johnzimm/xx-puppetboard