Add initial `.search_best()` and `.search_exact()`
Change out Exception types to match C-ext
Cleanup some internals with Node/Prefix
Rename lookup to add
Add .remove(), fix some _prefix bugs, cleanup iterator
Fix masking on prefix creation
Modify testcase to simply check for partial classname
Add pickle back and fix off-by-one bug
Correct a few off-by-one errors and mis-naming
More testing with travis