Requests 0.3.1

There are no library changes in this release. This release is signed with my PGP
key and includes the updated CHANGELOG and README.

Requests 0.3

v0.3.0 (2019-07-14)

New

• The URLSession perform extension now uses the Result type in the standard
  library.
• A new RequestTransportError type has been introduced. This type makes it
  easier to pass around contextual information with an error (e.g., the failing
  request, any received response).
• Added support for validating the received HTTPURLResponse in the
  URLSession perform extension.

API Breaking Changes

• Requests now requires Swift 5.
• The URLSession perform extension now uses the Result type in the standard
  library.
• The RequestError.invalidRequest error case has been removed and replaced
  with a standalone InvalidRequestURLError type.
• The RequestError.nonHTTPResponse error no longer wraps the received URLResponse

Requests 0.2

New

• Added a BodyProvider type that can generate the body of a request. This
  replaces the raw body data that was previously provided by a
  RequestConvertible type. A BodyProvider wraps a throwing function that
  generates a RequestBody and updates a Header. Built-in body providers are
  included for:
  • JSON bodies
  • Plain text bodies
  • Stream bodies
  • Raw data bodies
• Added an AuthenticationProvider type that can add authentication credentials
  to the header of a request. An AuthenticationProvider wraps a function that
  updates a Header instance. Built-in authentication providers are included
  for:
  • HTTP Basic authentication.
  • Bearer token authentication.
• Added a setter subscript to the Header type that can set a Field.

API Breaking Changes

• Requests now requires Swift 4.2
• The httpBody property has been removed from the RequestConvertible
  protocol. It is replaced by the bodyProvider property. This will silently
  break existing code.
• Header fields are now backed by a CaseInsensitiveString type instead of a
  String.
• The contentType and accept Fields now accept a MediaType instance
  instead of a string.