Add .run command

.run executes semicolon-separated commands in a file, as opposed to
newline-separated commands like .read.

(Still trying to figure out how to write the tests for this... any hints?)

Closes #4
as explained above instead of splitting by semi colon, let sql server do the work of splitting and running it separately, we can use runQuery helper here.

It may need to be modified as I think multiple commands may cause its callback to be fired multiple times, so we have to make sure  we output the result for each query correctly.