Closes #3 (IntervalTree.search raises exception when tree is empty)
Added test for issue 4 [ci skip]
Fixed intervaltree balancing (Issue #4)
Typo
all tests pass, but slowly
beginning merge of node.py with knode.py to mnode.py
PEP8: mnode
made list interpretation a generator
simplified Node.hit_branch()
more descriptive changelog for 0.4
speed: x is None -> not x
non-recursive add and remove