[TASK] Add travis caches, nodejs versions and virtualization
[TASK] Add travis caches, nodejs versions and virtualization

hopglass/ffrgb-meshviewer,ffrgb/meshviewer,freifunkMUC/meshviewer,freifunkMUC/meshviewer,ffrgb/meshviewer,FreifunkBremen/meshviewer-ffrgb,hopglass/ffrgb-meshviewer,Freifunk-Rhein-Neckar/meshviewer,FreifunkMD/Meshviewer,rubo77/meshviewer-1,xf-/meshviewer-1,Freifunk-Rhein-Neckar/meshviewer,xf-/meshviewer-1,Freifunk-Troisdorf/meshviewer,FreifunkMD/Meshviewer,Freifunk-Rhein-Neckar/meshviewer,Freifunk-Troisdorf/meshviewer,FreifunkBremen/meshviewer-ffrgb,rubo77/meshviewer-1