v0.5.0

Storage ergonomics. Applications can now use Dropbox through a compact,
object-storage-style API while the complete Dropbox-specific surface remains
available under Magpie.Files and the other namespace modules.

Added

• Magpie.Storage with put, get, streaming download, delete,
  exists?, stat, eager list, lazy stream, temporary download URLs and
  one-use upload URLs
• Explicit upload sources: {:file, path}, {:binary, iodata} and
  {:stream, enumerable}; streams use upload sessions and are rechunked
  without accumulating the whole input in memory
• Bang variants for storage operations, convenient for scripts
• Magpie.Files.upload_data/4, upload_stream/4 and download_file/3
• Magpie.Error.not_found?/1, conflict?/1, rate_limited?/1, auth?/1
  and retryable?/1

Changed

• Large file uploads now send their final partial chunk with the upload
  session commit request
• The public roadmap and its README link were removed