Use sql-simple-parser to validate queries

Solves https://github.com/zalora/redsift/issues/13 and https://github.com/zalora/redsift/issues/12

Drawbacks: limits in user queries are not supported (actually they never were ;-P)
I find the error output a bit ugly. Currently it looks something like this:
```
<query>:1:12:
select a as
           ^
"<query>" (line 1, column 12):
unexpected end of input expecting whitespace or identifier
```
Can we get that a bit nicer? We don't need the error location twice, we don't need the source (`<query>`) at all.