Use 3 build stages for Travis
Use 3 build stages for Travis

The 3 stages are:
- lint (1 job) for `flake8` and `planemo shed_lint`
- test (3 jobs) for `planemo test`
- deploy (1 job) for `planemo shed_update` to TTS and MTS

Also:
- Cache pip files
- Use `--conda_auto_install` option of `planemo test` instead of running
  `planemo conda_install` beforehand. This will install only the tool
  dependencies required by the tools tested in the job

xref. https://github.com/galaxyproject/tools-iuc/pull/1316#issue-230036801

blankclemens/tools-iuc,bimbam23/tools-iuc,pjbriggs/tools-iuc,abretaud/tools-iuc,blankenberg/tools-iuc,natefoo/tools-iuc,Delphine-L/tools-iuc,blankenberg/tools-iuc,gvlproject/tools-iuc,nekrut/tools-iuc,lparsons/tools-iuc,pjbriggs/tools-iuc,pjbriggs/tools-iuc,lparsons/tools-iuc,Delphine-L/tools-iuc,jj-umn/tools-iuc,natefoo/tools-iuc,mblue9/tools-iuc,galaxyproject/tools-iuc,blankenberg/tools-iuc,davebx/tools-iuc,blankenberg/tools-iuc,galaxyproject/tools-iuc,galaxyproject/tools-iuc,mvdbeek/tools-iuc,abretaud/tools-iuc,gvlproject/tools-iuc,davebx/tools-iuc,pavanvidem/tools-iuc,nekrut/tools-iuc,gregvonkuster/tools-iuc,Delphine-L/tools-iuc,galaxyproject/tools-iuc,gregvonkuster/tools-iuc,davebx/tools-iuc,galaxyproject/tools-iuc,dpryan79/tools-iuc,nekrut/tools-iuc,mvdbeek/tools-iuc,jj-umn/tools-iuc,dpryan79/tools-iuc,gvlproject/tools-iuc,blankenberg/tools-iuc,SANBI-SA/tools-iuc,dpryan79/tools-iuc,ieguinoa/tools-iuc,Delphine-L/tools-iuc,pavanvidem/tools-iuc,gregvonkuster/tools-iuc,mvdbeek/tools-iuc,gvlproject/tools-iuc,ieguinoa/tools-iuc,mblue9/tools-iuc,loraine-gueguen/tools-iuc,nsoranzo/tools-iuc,mvdbeek/tools-iuc,Delphine-L/tools-iuc,pavanvidem/tools-iuc,bimbam23/tools-iuc,davebx/tools-iuc,nekrut/tools-iuc,martenson/tools-iuc,davebx/tools-iuc,loraine-gueguen/tools-iuc,loraine-gueguen/tools-iuc,dpryan79/tools-iuc,loraine-gueguen/tools-iuc,nsoranzo/tools-iuc,lparsons/tools-iuc,blankclemens/tools-iuc,mblue9/tools-iuc,ieguinoa/tools-iuc,abretaud/tools-iuc,abretaud/tools-iuc,davebx/tools-iuc,mblue9/tools-iuc,blankenberg/tools-iuc,gvlproject/tools-iuc,nsoranzo/tools-iuc,blankclemens/tools-iuc,jj-umn/tools-iuc,pjbriggs/tools-iuc,pavanvidem/tools-iuc,pjbriggs/tools-iuc,davebx/tools-iuc,jj-umn/tools-iuc,lparsons/tools-iuc,nsoranzo/tools-iuc,mvdbeek/tools-iuc,abretaud/tools-iuc,gregvonkuster/tools-iuc,pavanvidem/tools-iuc,Delphine-L/tools-iuc,natefoo/tools-iuc,pavanvidem/tools-iuc,nsoranzo/tools-iuc,natefoo/tools-iuc,galaxyproject/tools-iuc,loraine-gueguen/tools-iuc,dpryan79/tools-iuc,jj-umn/tools-iuc,gregvonkuster/tools-iuc,SANBI-SA/tools-iuc,bimbam23/tools-iuc,jj-umn/tools-iuc,nekrut/tools-iuc,nekrut/tools-iuc,jj-umn/tools-iuc,blankclemens/tools-iuc,natefoo/tools-iuc,mblue9/tools-iuc,mvdbeek/tools-iuc,ieguinoa/tools-iuc,SANBI-SA/tools-iuc,lparsons/tools-iuc,loraine-gueguen/tools-iuc,ieguinoa/tools-iuc,dpryan79/tools-iuc,pavanvidem/tools-iuc,nekrut/tools-iuc,ieguinoa/tools-iuc,gvlproject/tools-iuc,gregvonkuster/tools-iuc,abretaud/tools-iuc,galaxyproject/tools-iuc,nsoranzo/tools-iuc,gregvonkuster/tools-iuc,SANBI-SA/tools-iuc,Delphine-L/tools-iuc,nsoranzo/tools-iuc,mvdbeek/tools-iuc,natefoo/tools-iuc,abretaud/tools-iuc,bimbam23/tools-iuc,loraine-gueguen/tools-iuc,bimbam23/tools-iuc,natefoo/tools-iuc,pjbriggs/tools-iuc,lparsons/tools-iuc,mblue9/tools-iuc,bimbam23/tools-iuc,ieguinoa/tools-iuc,blankenberg/tools-iuc