contract for `open' does not match documentation

[cobbe]

The docs for `open' state that the function's contract is

((or/c path-string? (symbols ':memory: ':temp:)) . -> . db?)

but the contract specified by the implementation is instead

((or/c path? (symbols ':memory: ':temp:)) . -> . db?)

As a result, `open' does not accept string inputs, even though the docs claim it does.

[jaymccarthy]

Will be fixed in next version