Undefine original adapter methods to fix warnings

Warnings are being thrown because Faraday's Typhoeus adapter is defined before the adapter internal to Typhoeus defines the same set of methods. This patch undefines the methods from Faraday's adapter before the Typhoeus adapter redefines them.

We'd only keep this around until the Faraday adapter is extracted into its own gem, which [should be happening](https://github.com/lostisland/faraday/issues/202) as part of the 1.0 release.

@i0rek