update gitignore file
mover bernoulli function signature test
moved and refactored binomial function_sig tests
refactor beta_binomial function-sig tests
moved hypergeometric function-sig tests
refactored distribution function signature tests for:

beta, cauchy, chi square, bernoulli, beta_binomial, binomial,
hypergeometric, neg_binomial, poisson
refactored distribution function signature tests for:

double_exponential, exp_mod_normal, exponential, gamma, gumbel,
inv_chi_square, inv_gamma, logistic, lognormal, normal
refactored distribution function signature tests for:

lognormal, pareto, rayleigh, scaled_inv_chi_square, skew_normal,
student_t, uniform, von_mises, weibull
refectored function_sig tests for:

categorical distr, dirichlet distr, multinomial distr, neg_binomial_2
distr, abs, int_step, min, max, operators
functions_signatures

i have  implemented some functions signatures
functions signatures

some functions signature
functions signature

functions signatures
signatures

dot_self, fdim, il_else, inv_sqrt, inv_square, log2
Some typos fixed in programming.tex
fixed typo in 12.3 ARM
Merge branch 'develop' of https://github.com/stan-dev/stan into develop
Merge branch 'develop' of https://github.com/stan-dev/stan into develop
merge develop
removed extra files
updated function signature tests