This should address issue #2 to use fallocate instead of dd to populate
the block file much faster than a ton of dd time.
Typo in last commit for #2 meant the path for the encrypted file was wrong.
fallocate doesn't work on enough filesystems to be useful, so I'm switching #2 to use truncate instead.
At least on EC2, it won't work for the ext3 filesystems in the Ubuntu base image.
truncate won't actually pre-allocate filesystem blocks, but otherwise works fine.
Merge pull request #3 from dyninc/truncate

Truncate