Output buffer re-use

[samcday]

Thanks for authoring this lib!

Currently I have to drop down to the unsafe lz4-sys bindings because the higher level stuff doesn't quite fit my use-case. My issue is that all the high level APIs are allocating the output buffer themselves. It would be ideal if the lz4::block::* methods had variants that allowed you to supply an output &mut [u8], and the lz4::Decoder / lz4::Encoder structs allowed you to supply an output Vec<u8>. What do you think? If you have some ideas on how you want the API to look I'm happy to whip up a PR.

[samcday]

e.g flate2 has this functionality

[jheyens]

Hi,
I actually intend to adjust the API to closely match flate2 for a 2.0 release. This is currently not very high on my priority list, though, so feel free to start.

[samcday]

I ended up going with the snap crate instead, since I wanted something that works for WebAssembly target. I'll leave this issue open in case someone else feels like tackling it though!