v0.7.0

• Changed: Split SimpleJWT\Crypt namespace into multiple namespaces, one
  for each algorithm type (#60)
• Changed: JWT and JWE now derives from a common parent class Token
• Changed: Improved ASN.1 processing code (#68)
• Changed: Util::base64url_decode() will now throw
  \UnexpectedValueException instead of returning false if the input
  cannot be decoded