Base64 is not urlsafe

[tomwaddington]

Google APIs (specifically Gmail Message.raw), use url-safe base64 encoding and decoding.

At https://github.com/google/autoparse/blob/master/lib/autoparse.rb#L199

Base64.decode64(value)

Should be

Base64.urlsafe_decode64(value)

to prevent decode errors. Same goes for the encoding!