v0.23.3

• Fix nvm ls v1.0.3 so that it locates iojs-v1.0.3.
• Bypass sha1sum/sha1 aliases. (#640)
• Ensure that nvm run 0.12 --version errors out sensibly when 0.12 isn't installed.
• Filter out the io.js version dir from nvm_ls output. (#642)