Support newer versions of firebase/php-jwt

[BVMiko]

After some testing, this package seems to work fine with PHP-JWT v5.0.

[lord2800]

I don't suppose you happen to have a link to the changelog handy?

[BVMiko]

PHP-JWT Changelog:

5.0.0 / 2017-06-26

• Support RS384 and RS512.
  See #117. Thanks @joostfaassen!
• Add an example for RS256 openssl.
  See #125. Thanks @akeeman!
• Detect invalid Base64 encoding in signature.
  See #162. Thanks @psignoret!
• Update JWT::verify to handle OpenSSL errors.
  See #159. Thanks @bshaffer!
• Add array type hinting to decode method
  See #101. Thanks @hywak!
• Add all JSON error types.
  See #110. Thanks @gbalduzzi!
• Bugfix 'kid' not in given key list.
  See #129. Thanks @stampycode!
• Miscellaneous cleanup, documentation and test fixes.
  See #107, #115,
  #160, #161, and
  #165. Thanks @akeeman,
  @chinedufn, and @bshaffer!

4.0.0 / 2016-07-17

• Add support for late static binding. See #88 for details. Thanks to @chappy84!
• Use static $timestamp instead of time() to improve unit testing. See #93 for details. Thanks to @josephmcdermott!
• Fixes to exceptions classes. See #81 for details. Thanks to @Maks3w!
• Fixes to PHPDoc. See #76 for details. Thanks to @akeeman!

[coveralls]

Coverage decreased (-0.1%) to 69.048% when pulling 9b942ac on BVMiko:master into 01a42fe on bigcommerce:master.

[lord2800]

Thanks! I'll see about getting this merged!