ENH: stats/_multivariate: implementation of multivariate normal variable
MAINT: mvn distn -- do not choke on large determinants, and make pinv and pdet agree on which singular values are small
TST: remove a call to a numpy function that is too new to use
MAINT: use a more standard python version compatibility preamble
MAINT: simplified parameter specification of multivariate_normal_frozen class

Suggestion by bburlo.
MAINT: changed wording in docstring to reflect order of return values
MAINT: replace einsum, using a decomposed precision matrix
MAINT: use eigh instead of svd
MAINT: trivial changes to docstring formatting
MAINT: implemented more careful handling of cutoff parameter
DOC: more explicit description for parameters in _logpdf
MAINT: explicit parameters in construction frozen class
TST: compare values of pdf with precomputed values
MAINT: create new multivariate_normal_gen instance in frozen class
MAINT: added 'rvs' member function to generate random samples
MAINT: mvn error checking
TST: random number seeds
DOC: param order
DOC: remove caveats about not checking that the matrix is positive semidefinite
DOC: partially undo overzealous doc deletion