Fix last set of missing v5 paths

[zikaeroh]

This fixes the paths that were missed in #561 (comment).

These _ prefixed folders are actually ignored by the Go tool when ran from an upper directory, so there's no imminent need. My comment was wrong, this is strictly for finishing the move.

Might be a good idea to add to the builder something that explicitly tries to build the files in _examples, to catch any errors.

[icholy]

@zikaeroh I've added a path subcommand to gomajor to help with upgrades like this in the future.

# increment the major version
$ gomajor path -next

# set the major version
$ gomajor path -version=v7

# change the whole module path (if you decide to move the repo to avoid SIV)
$ gomajor path chisite.io/chi