[WIP] ARROW-4463: [Rust] Add Feather read:write support

[nevi-me]

Adds the ability to convert feather files to and from record batches.

[nevi-me]

@andygrove @sunchao @paddyhoran PTAL when convenient, I'm largely looking for review and guidance on the API, and parts of the code that I can DRY.

@wesm I looked at the Feather repo, as well as within Arrow to see whether Feather is still supported or should be regarded as deprecated. I'm still unsure of what the case is.

I know that there's Arrow File format in IPC, but I opted to start with Feather (with the intent that we'd be able to reuse most of the code when implementing Arrow RPC in Rust) as I had an immediate need for being able to write Arrow files to memory.

[wesm]

I responded on the JIRA. The internal details of the current Feather format should be regarded as deprecated. I would recommend trying to repurpose as much of your work here in supporting the more general Arrow IPC protocol. If you want to maintain support for the legacy Feather format for now that's your choice ;)