Allow raw queries to be posted to HTTP API.

This change allows SkyQL queries to be posted directly through the HTTP API like this:

```
$ curl localhost:8585/tables/awesomeness/query -d "SELECT count() AS count"
```

Or with a file:

```
$ curl localhost:8585/tables/awesomeness/query --data-binary @myquery.skyql
```

Make sure you use `--data-binary` if you're using cURL. Otherwise cURL strips out your newlines which sucks.

/cc: @orenmazor @boourns @snormore