Fix parameter name on Newsletter List Get Call

Parameter for searching for a specific email on a specific list should be `email` and not `get`
Merge pull request #489 from scottkawai/patch-1

Fix parameter name on Newsletter List Get Call
fixed markdown/html encoding issues

fixed some issues with markdown not being parsed as introduced in
pr #473
Add ruby wrapper for Template Engine API
Merge pull request #491 from awwa/patch-3

Add ruby wrapper for Template Engine API
Merge pull request #492 from sendgrid/develop

deploy ✈️