Error with byte sequence 0xe2 0x80 0x99 in a latin1 postgres db
### Summary

i've been receive an error when i try to connect postgraphile in a postgres 9.5 encoded with LATIN!

### Actual results

this is the log of problem when i try to execute postgraphile by docker

error: character with byte sequence 0xe2 0x80 0x99 in encoding "UTF8" has no equivalent in encoding "LATIN1"
    at Parser.parseErrorMessage (/postgraphile/node_modules/pg-protocol/dist/parser.js:287:98)
    at Parser.handlePacket (/postgraphile/node_modules/pg-protocol/dist/parser.js:126:29)
    at Parser.parse (/postgraphile/node_modules/pg-protocol/dist/parser.js:39:38)
    at Socket.<anonymous> (/postgraphile/node_modules/pg-protocol/dist/index.js:11:42)
    at Socket.emit (events.js:314:20)
    at addChunk (_stream_readable.js:297:12)
    at readableAddChunk (_stream_readable.js:272:9)
    at Socket.Readable.push (_stream_readable.js:213:10)
    at TCP.onStreamRead (internal/stream_base_commons.js:188:23)


### Additional context

### Possible Solution

i check character correspondence of byte 0xe2 0x80 0x99 and caracter is ’, postgresgraphile is not able to check latin encoded dbs or maybe this can be a problem with comments of sql who have this caracters?
