Implement creation of self signed jwt for assertion based auth.
Fix bug in self signed JWT creation.  The header must contain the cert thumbprint.  The jwt-simple lib doesn't provide a way to do that.  Switching to customer implementation.
This should have been part of the last commit, 354704bba47babd3de39583a6d86fc6965a4897a.
Tests were broken by a change in the nock package.  This fixes the issue by trimming the path from any hosts passed to nock.
Get basic cert auth happy path implemented.
Merge branch 'dev' into cert_auth

Conflicts:
	test/util/util.js
Update basic self-signed-jwt test to actually check that the returned jwt matches what was expected given static inputs.
Complete self-sign-jwt validation code and tests.
Add end to end tests for client assertion flow.
Add sample for certificate/client assertion flow.
Update logging message that was cut and pasted.
Merge pull request #32 from RandalliLama/dev

Add support for certificate based confidential client auth.  acquireTokenWithClientCertificate