add lorem.clj/lorem.txt for some simplistic benchmarking

(On my system macro-expanded template-fn produces functions
which are slightly slower than those produced by
template-fn* for this particular example.)
approximately double the speed of macro-compiled templates

We're now generating interop code directly to create a
StringBuilder and make calls to .append.
improve performance by precomputing correct capacity for StringBuilder

For lorem.txt, this seems to nearly double performance. (The effect is
very sensitive to the quality of the estimate.)