Add macOS support

• Add macOS support
• Add macOS target to Travis CI
• 1b36303 Force conversion of lockbox dir to absolute path

Verify correct decryption using manifest

• 4dd97f1 Allow user to view decryption progress
• 935646b Rework parameter handling
• f655a77 Add concept of manifest to verify correct decryption

8K chunks

Make dd write data in 8K chunks, to match OpenSSL enc bsize

Initial release

v1.0.0

Update README