Fix (and test coverage) for base64 encoding issue.
Fix (and test coverage) for base64 encoding issue.

stefanw/flanker,mailgun/flanker,aroberts/flanker,nylas/flanker,alex/flanker,glyph/flanker,EthanBlackburn/flanker,xjzhou/flanker,smokymountains/flanker,EncircleInc/addresslib,ad-m/flanker