v0.10.0-alpha.1

• Add std::future::Future support.
• Add wasm32-unknown-unknown support (with fewer features).
• Add ability to pass async Response as the body of another Request.
• Change default Client API to async. The previous blocking client API is avaialble at reqwest::blocking.
• Change default feature set to reduce unnecessary dependencies. Most features are disabled by default:
  • blocking: The reqwest::blocking (synchronous) client API.
  • cookies: Cookie store support.
  • gzip: Automatic response body decompression.
  • json: Request and response JSON body methods.
• Change futures::Stream support to a disabled-by-default unstable-stream feature.
• Change Error internal design, removing several Error::is_* inspector methods.
• Update url to v2.0.