Fix require-sql to use . instead of / in internal ns name

[joelittlejohn]

It appears that the require-sql macro doesn't currently work, as it places the functions it defines into an invalid namespace.

Using the macro like:

(require-sql ["queries.sql" :as foo])
(foo/my-query ...)

Results in:

java.lang.IllegalStateException: Attempting to call unbound fn: #'yesquire/queries.sql/my-query

since the internal namespace created to hold the functions has an invalid char / within it (yesquire/queries.sql).

The tests in yesql.core-test also exhibit this problem, but since the functions aren't invoked the problem isn't obvious.

This change fixes the internal namespace in which the query functions are placed by using . rather than / chars in the ns name. I've also added an actual invocation of the declared query fns into the test to verify that the functions can be called.

[joelittlejohn]

@iantruslove would you be able to take a quick glance at these changes and give this a thumbs-up if you think it's good to merge? Please shout if you think there's something I'm missing about this.