dmbates/MixedModels.jl: Fix loglikelihood calculation with weights

Fixes #89 Adds more benchmarks Introduces and uses model_response(mf::ModelFrame, d::Distribution) to convert a binary PooledDataArray response to a 0/1 floating point vector. This should be done in DataFrames and a pull request will be made for this. pass the random number generator to the simulate! method methods for A_rdiv_Bc!, etc. that are now in Base are commented with if VERSION < ... allow a contrasts specification in lmm and glm