Added version comparison and tests

[cjrolo]

Closes #146

This PR addresses issue #146 in the following way:

1. Adds Version information in the CompressorHeader (Extracted from Cargo.toml)
2. On Decoding checks the version of the file against the version of the compressor.
   2.1 Doesn't allow decompression of higher version files by lower version compressor (Should it?)
3. Add tests for the compression/decompression
4. Minor version bump to start tagging the files where the header was introduced.

[worryg0d]

LGTM! I left some nits regarding some code duplications and little optimization.

2.1 Doesn't allow decompression of higher version files by lower version compressor (Should it?)

I think so. The frame format may be changed in the future, so parsing them with an outdated compressor version may lead to undefined behavior.

[worryg0d]

Nit: Both decode and borrow_decode contain the same code for verifying the version field. Making a func for this looks reasonable to me.

fn verify_header_versions(header: &CompressorHeader) {
    let current_version = env!("CARGO_PKG_VERSION").to_string();
    trace!("Versions: c:{} h:{}", current_version, header.version);
    match compare(&current_version, &header.version) {
        Ok(Cmp::Lt) => panic!(
            "Can't decompress! File is version ({}) is higher than compressor version ({})!",
            header.version, current_version
        ),
        Ok(Cmp::Eq | Cmp::Gt) => debug!("File version: {}", header.version),
        _ => panic!("Wrong version number!"),
    }
}