Change: Executor to be a generic module

Previously, the Executor daemon was intended to be subclassed for
each new kind of profiler. Given that profilers expose a standardized
interface there is no need for multiple executors.

Signed-off-by: Kevin Conway <kevinjacobconway@gmail.com>
Merge pull request #17 from kevinconway/generic_executor

Change: Executor to be a generic module