Update cloudmig's code to compile with version 3.0 of libdroplet.
Older versions are now unsupported (Too many API changes).

Resolves issue #33, as well a prepare the ground for a proper ACL
replication from source to destination (since the new APIs now
offer a proper support).
Fix issue #7 of Scality's cloudmig repo (Cmake FindDot re-runs find_program).

The patch was proposed by trombonehero(github)
Issue #34: Notify known bug in manual page.
Merge pull request #8 from Joacchim/master

Fix compilation against droplet v3.0 and issue #7