Version Bump v4.2.1: Update to latest Jackson recommended dependency

Version Bump v3.2.2: Update to latest Jackson recommended dependency

Version Bump v4.2.0: Hacktoberfest rollup release

Version Bump v4.1.2: PR sendgrid#220 Alway serialize click-tracking p…

…arameters

Version Bump v4.1.1: PR sendgrid#247 Added Javadocs.

Version Bump: v4.1.0: PR sendgrid#211 Return empty collections in pla…

…ce of nulls

Version Bump v4.0.1: PR sendgrid#199 Return correct Email in getFrom

Version Bump v4.0.0: PR sendgrid#162 Update java http client dependen…

…cy to 4.1.0 from 2.3.4

Version Bump v3.2.1: sendgrid#175 Simplified method.

Version Bump v3.2.0: sendgrid#160 Adds an attachment builder that sup…

…ports InputStream content