v 0.3.5 Bug fixes and improvements

- fail gracefully when an error response doesn't include JSON error
  fields
- webmention HTTP request tweaks
- use requests.apparent_encoding
Merge branch 'master' of github.com:vrypan/webmention-tools
Vesion 0.3.6: Bug fixes and improvements

- fail gracefully when an error response doesn't include JSON error
  fields
- webmention HTTP request tweaks
- use requests.apparent_encoding
- handle relative endpoints. fully qualify them with the target scheme
  and host