docs: ubuntu iso's hybrid format and parted warnings (#585)
docs: ubuntu iso's hybrid format and parted warnings (#585)

Document that `parted` warnings about invalid GPT and physical block
size issues can be safely ignored as they are a consequence of "hybrid
iso's".

Fixes: https://github.com/resin-io/etcher/issues/312
Signed-off-by: Juan Cruz Viotti <8493db2a4f45d66df375afe12f7eba59fe1c8d78@gmail.com>
resin-io/etcher,resin-io/etcher,resin-io/herostratus,resin-io/etcher,resin-io/etcher,cedricve/etcher,cedricve/etcher,resin-io/etcher,resin-io/resin-etcher,cedricve/etcher,resin-io/herostratus,resin-io/resin-etcher