Fix statement interruption

Fix syntax for interruptStatement method to refer to correct `conn` object.

Fix SQL statement for interruptStatement to use `statementID` variable (not SQL column).

Add unit test to verify statement interruption.

NOTE:
  Unforunately, the normal testing method using `SELECT SLEEP(1000)` does
  not work since `SLEEP` statements are not interruptible. See
  connection_test.coffee for more comments.

Coffeescript modifications only. Javascript not built.
remove whitespace.
Merge pull request #40 from themadcreator/master

Fix statement interruption