Refactored smells out of query_runner/driver.rb

Smells reported by reek:

Before:

 1: NoBrainer::QueryRunner::Driver has no descriptive comment
    (IrresponsibleModule)
 5: NoBrainer::QueryRunner::Driver#call calls NoBrainer.connection
    twice (DuplicateMethodCall)
 4: NoBrainer::QueryRunner::Driver#call calls env[:query] twice
    (DuplicateMethodCall)
 7: NoBrainer::QueryRunner::Driver#call has the variable name 'e'
    (UncommunicativeVariableName)

After:

 1: NoBrainer::QueryRunner::Driver has no descriptive comment
    (IrresponsibleModule)

Notes:

Fairly trivial changes again. Extract method and local variables.