Lower bound when converged

[michaelbynum]

galini/galini/branch_and_bound/tree.py

Line 243 in 56a80fb

new_lower_bound = self.state.upper_bound

Should this use self.state.lower_bound instead of self.state.upper_bound? Currently, if there are not any open nodes, then the lower bound gets set to the upper bound passed to this method.