remove the 'v' prefix from iojs version names
remove the 'v' prefix from iojs version names

following the pattern of node version names (which are just the bare
version number), strip the leading v from iojs version names.

so iojs-v1.0.0 -> iojs-1.0.0 (both in filename, and install listing)

jasonrhodes/node-build,platanus/node-build,pongstr/node-build,nodenv/node-build,brigade/node-build,OiNutter/node-build,dark5un/node-build,joshuarubin/node-build