Update parser.ex

[nacengineer]

Fix deprecation warning of use instead of import

[tiagopog]

@nacengineer let's take the opportunity to fix this in the Encoder module as well.

[tiagopog]

@devinus This a really simple and harmless change that will help the community to avoid debugging issues in CI builds when warnings are treated as errors. Thanks in advance!

[ryvasquez]

I've open the same PR last year https://github.com/devinus/poison/pull/208 but still not yet merged