Make Term#recalculate_value define value in full

Using a calculator and assuming summation is less preferable because in some
cases summation may not be the desired outcome, and there is no need to
outsource the calculation when a subclasses are available.  This will allow
specific calculations to be optimized according to the algorithm; in other
words making Term the caching object that it wants to be.
Ignore DS_Store
Update benchmarks
Cleanup initialization signatures and naming

Identifer is better than name here because later it will be used as a read id
for the node (implication => unique-ish).  Also makes it clear data can be
anything by setting the default to nil.
Use a rounder number in the core bench

11, really?
Add some setup/run instructions for testing on VM

Specifically a debian instance on google compute.