Handling of empty files

[mbhall88]

needletail/src/parser/mod.rs

Line 53 in cd12c12

reader.read_exact(&mut first_two_bytes)?;

This line will cause an error to be returned for an empty file. Is this a feature or a bug?

Effectively, I'm asking if you intentionally return an error for empty files?

I personally don't like failing on empty files. I wonder if you would consider adding a ParseErrorKind variant for an empty file so I can identify and handle these cases accordingly in my project?

I'm happy to implement if you're short on time, but wanted to check first if this is inline with your library.

[Keats]

IIRC it's intended, we consider empty files to be invalid in our codebases. I think a specific ParseErrorKind would be nicer than a IO error though. A PR would be welcome.

[mbhall88]

@Keats do you think I might be able to get a review on #52 at some point? I appreciate you probably have lots of other things happening so if you don't have time that is ok.