Add fixStack method

- Before sending a query to the server we use a dummy stack container
  to get the current stack trace and store it in the closure
- When a query has an error this method can be used to replace the
  current stacktrace with the stacktrace from the closure
- At the same time the first line in the stack trace ([object Object])
  will be replaced with the actual exception name and message
- The stack trace at the point where the error is discovered only
  contains references to node-cassandra-cql and is therefore not
  helpful for the user to figure out which part of his own code caused
  the error
Save stacktrace before sending query

- Save the stacktrace on the way down into the call stack and restore
  it to eventual errors on the way back out to the caller
Merge branch 'query_and_stack_on_errors' of https://github.com/sgronblo/node-cassandra-cql into query_and_stack_on_errors
Appended original stack trace before tick
Added contributor