Changelog for hjsonschema-0.5.3.1

# 0.5.3 + Switch from http-conduit to http-client. # 0.5.2 + Add convenience function for validating and compiling draft 4 schemas simultaneously. # 0.5.1 + Switch from wreq to http-conduit; drop lens dependency. # 0.5 + Start changelog. + Rename Utils.hs to Helpers.hs. + Move all non-ValidatorGen functions in Validators.hs to Helpers.hs. + Various touchups.