Equations added

This partially addresses issue #321 by adding these equations: ace, enspie, heip_e, fisher_alpha, kempton_taylor_q, mcintosh_e, menhinick, shannon, simpson, and strong. In addition, variable definitions were added to berger_parker_d and to brillouin_d. 
Each function's docstring needs to have a single sentence summarizing what it does, and this summary has to fit within the 80-character limit on a single line. Below this summary line you can add a longer description with the equation, etc. Can you please update here and in the other functions that you modified?