Main branch has problems:

• Currently we have the sketches factor option in the configuration but it doesn't affect anything... oops.
• When our threads throw an exception this can cause a race case resulting in memory errors instead of exiting gracefully.
• log2(const expr) is not always a const expr with all compilers.
• The pre_insert function builds a representation of the entire graph on an insert only stream. yikes. Instead we want to just maintain the spanning forest edges.

This pull request fixes all of those problems.