fixed binom_coeff_log in fvar with tests
added lmgamma to fvar (without tests)
added var as reserved variable in var_decls_grammar_def.hpp and in doc in language.tex
added operator< and Phi functions with simple tests
 added comparison operators <=, >, >=, !=, == with tests
fixed lmgamma in fvar with tests
removed Mac folder customization file
new autodiff.hpp for functor-based derivatives
added Jacobian and Jacobian with reverse mode to autodiff
added Hessian to functor-based autodiff with test
added general gradient using only fvar
added polymorphic Hessian using only fvars with test
added gradient extraction to hessian functions
added derivative and partial derivative functions for autodiff
added gradient of trace of matrix times hessian for RM-HMC
added numeric_limits for fvar but not fully tested yet
fixed numeric_limits for fvar and added tests
merge
refactoring fvar
refactor fvar; runs all fvar tests