Remove dependency on commons-codec.

[christopherthielen]

I see there's already some discussion regarding whether or not it's a good idea to keep Jackson as a dependency. Considering it currently is a dependency, however, it's worth noting that Jackson also provides Base64 en/decoding. This PR removes the commons-codec dependency and replaces the en/decode calls with a small Base64 class that delegates to Jackson.

All current tests pass.

I'm packaging and deploying original-java-jwt.jar (no dependencies rolled in via shade) into my app. I don't really want a dependency on commons-codec, thus the motivation for this. It's just a thought 👍

[pose]

Thanks @christopherthielen. We like the idea of replacing codecs dependency but we need to make some checks in order to see if it works as expected.

[schmitch]

Is this really necessary?! I mean Java8 has a Base64 decoder, so basically people could just use it and force a Version which only works on Java8

[sibay]

i saw this pr too late. i just added a new pr replacing commons-codec and jackson with jdk8 base64 and boon json. Someone should decide what to take.