TST: travis: add required packages
TST: travis: add required packages

Travis requires the "SWIG" and "numpy" packages to be
installed before installing "scikit-umfpack." In the case 
where "NUMPYSPEC=" (i.e. numpy should not be installed
numpy is installed and then uninstalled before and after
installing "scikit-umfpack".

Closes #7940.
jor-/scipy,e-q/scipy,grlee77/scipy,andyfaff/scipy,ilayn/scipy,jamestwebber/scipy,pizzathief/scipy,WarrenWeckesser/scipy,aarchiba/scipy,lhilt/scipy,Stefan-Endres/scipy,anntzer/scipy,jamestwebber/scipy,tylerjereddy/scipy,Eric89GXL/scipy,aarchiba/scipy,person142/scipy,scipy/scipy,e-q/scipy,Stefan-Endres/scipy,rgommers/scipy,zerothi/scipy,perimosocordiae/scipy,matthew-brett/scipy,nmayorov/scipy,vigna/scipy,matthew-brett/scipy,vigna/scipy,mdhaber/scipy,tylerjereddy/scipy,Eric89GXL/scipy,zerothi/scipy,rgommers/scipy,aeklant/scipy,andyfaff/scipy,mdhaber/scipy,mdhaber/scipy,person142/scipy,rgommers/scipy,arokem/scipy,pizzathief/scipy,jor-/scipy,Eric89GXL/scipy,pizzathief/scipy,scipy/scipy,person142/scipy,person142/scipy,aarchiba/scipy,nmayorov/scipy,lhilt/scipy,nmayorov/scipy,perimosocordiae/scipy,aeklant/scipy,tylerjereddy/scipy,aeklant/scipy,jor-/scipy,ilayn/scipy,anntzer/scipy,Eric89GXL/scipy,Stefan-Endres/scipy,gertingold/scipy,gfyoung/scipy,arokem/scipy,WarrenWeckesser/scipy,pizzathief/scipy,perimosocordiae/scipy,jamestwebber/scipy,Eric89GXL/scipy,matthew-brett/scipy,perimosocordiae/scipy,WarrenWeckesser/scipy,e-q/scipy,rgommers/scipy,endolith/scipy,endolith/scipy,grlee77/scipy,grlee77/scipy,aarchiba/scipy,vigna/scipy,endolith/scipy,endolith/scipy,gertingold/scipy,person142/scipy,gfyoung/scipy,perimosocordiae/scipy,WarrenWeckesser/scipy,vigna/scipy,scipy/scipy,scipy/scipy,gfyoung/scipy,andyfaff/scipy,mdhaber/scipy,e-q/scipy,arokem/scipy,zerothi/scipy,gertingold/scipy,zerothi/scipy,aeklant/scipy,endolith/scipy,andyfaff/scipy,zerothi/scipy,Stefan-Endres/scipy,gertingold/scipy,aeklant/scipy,arokem/scipy,zerothi/scipy,gfyoung/scipy,ilayn/scipy,vigna/scipy,andyfaff/scipy,tylerjereddy/scipy,jor-/scipy,rgommers/scipy,WarrenWeckesser/scipy,anntzer/scipy,Eric89GXL/scipy,aarchiba/scipy,grlee77/scipy,WarrenWeckesser/scipy,lhilt/scipy,pizzathief/scipy,matthew-brett/scipy,matthew-brett/scipy,e-q/scipy,lhilt/scipy,grlee77/scipy,scipy/scipy,gertingold/scipy,perimosocordiae/scipy,anntzer/scipy,mdhaber/scipy,gfyoung/scipy,ilayn/scipy,ilayn/scipy,Stefan-Endres/scipy,ilayn/scipy,lhilt/scipy,jamestwebber/scipy,tylerjereddy/scipy,nmayorov/scipy,andyfaff/scipy,Stefan-Endres/scipy,jor-/scipy,jamestwebber/scipy,nmayorov/scipy,mdhaber/scipy,scipy/scipy,anntzer/scipy,endolith/scipy,arokem/scipy,anntzer/scipy