bump convict: 0.5.1 => 0.6.1
bump convict: 0.5.1 => 0.6.1

Pick up convict's latest dependecies (i.e, validators) and other bug
fixes.

bloomberg/blpapi-http,flojdek/blpapi-http,bloomberg/blpapi-http,bloomberg/blpapi-http,flojdek/blpapi-http,fyquah95/blpapi-http,fyquah95/blpapi-http,fyquah95/blpapi-http,flojdek/blpapi-http,flojdek/blpapi-http,flojdek/blpapi-http