r_test_c: Residual randomization test
In RRI: Residual Randomization Inference for Regression Models

Implements the residual randomization test. The hypothesis tested is

1	r_test_c(y, X, lam, lam0, cluster_eps_r, use_perm, use_sign, num_R)

`y`	Vector of outcomes (n x 1).
`X`	Matrix of covariates (n x p). First column should be 1's.
`lam`	Vector of coefficients in linear H0 (p x 1).
`lam0`	Scalar value for linear H0.
`cluster_eps_r`	A `List` with restricted residuals. See get_clustered_eps.
`use_perm`	`Boolean` flag whether to use permutations within clusters.
`use_sign`	`Boolean` flag whether to use sign flips across clusters.
`num_R`	Integer of how many randomization values to calculate.