Get rid of parameters

[OxSon]

For ease of testing, it's nice to be able to change the branch factor / max width of a tree (it's much easier to write out a manual test for a 2 or 4-way branching tree than a 32-way branching tree), but in the end, this configuration capability is probably not needed and also probably negatively affects performance. What Clojure does is maintain separate copies of the code where one is parameterized and one is not (see here). We could do something like that, if maintaining parameterized capability is desired (maybe for future dev work / testing, maybe there is some actual production code use case)

• change [this stuff] (https://github.com/OxSon/rrb.rhm/blob/use_array/rrbtree.rhm#L12) to just be constants rather than Parameters
• adjust tests to remove with_shift_inc(....) stuff