adjust file heirarchy to use cmd/allmark

[urandom2]

The use of the cli directory works, but makes go-get painful to use. This change adopts the standard cmd directory for main packages, and allows for go get github.com/andreaskoch/allmark/cmd/allmark.

Note this is a breaking change, as go get github.com/andreaskoch/allmark/cli will not do what it did before.