Various minor improvements

[lgoldstein]

• Promote methods visibility - for easier use by code that wants to use the same parameters as the encryptor/decryptor
• Expose wrapSource/targetStream for code that needs to encrypt streams instead of files - to allow callers to optimize their streams accordingly
• Use try-with-resource for clearer code
• Use absolute paths to ensure file not encrypted/decrypted onto itself

[justinludwig]

Nice! I merged, and also added a quick javadoc one-liner to the newly-public methods that didn't have any javadocs yet.

[lgoldstein]

Great thanks.