0.1.0: Update to sentry-native 0.4.0 and first release.

Added

• Added support for changing the backend.
• Added support for Android.
• Added support for userdata for Options::set_logger through the Logger
  trait.
• Added Options::set_auto_session_tracking and
  Options::auto_session_tracking.
• Added missing documentation for session_start and session_end.

Changed

• Replaced user_consent_give, user_consent_revoke and user_consent_reset
  with set_user_consent.
• Renamed user_consent_get to user_consent.
• Renamed feature default-transport to transport-default and
  custom-transport to transport-custom.
• Updated sentry-native to 0.4.0.
• Changed the default backend for Linux to Crashpad.
• Changed the default transport for Android to Curl.
• Changed set_transport's startup argument to return Result and fail
  Options::init if Err is returned.

Fixed

• Fixed thread-safety in almost all functions that could otherwise crash the
  application or cause undefined behaviour.
• Improved naming of libraries in the documentation.
• Exclude some folders from the included Sentry Native SDK that are only
  relevant for testing from the Crates.io package. This not only reduces the
  size of the overall package, but also helps to avoid issues with Windows's
  maximum path length.
• Improved README.
• Fixed unnecessary include of the WinHttp library when the default transport is
  disabled.
• Fixed set_http_proxy documentation to state that the full scheme is
  required.
• Fixed Transport::send documentation to state that envelopes have to be sent
  in order for sessions to work.