ENH sparse: Add Ellipsis indexing to sparse matrices.
TST sparse: Add tests Ellipsis indexing with sparse matrices.
TST: add the Burkardt test matrices for the matrix exponential
MAINT: math.expm1 -> np.expm1 hoping for compatibility with old python/numpy
MAINT: avoid an overflow in rice pdf
MAINT: change von Mises support to [-pi, pi]
TST: test generic _entropy vs distribution-specific implementations
BUG: fix _entropy for gumbel, logistic distributions.
TST: fix the _entropy tests (inheritance), silence the fp errors
TST: re-enable tests for the wald distribution
BUG: fix _entropy for the gamma distribution
MAINT: remove unnecessary comments
Revert "MAINT: change von Mises support to [-pi, pi]"

This reverts commit 024ce0b65b1e1c6c06a2345e13d317cbd5757b1f.
DOC: add a note to the vonmises docstring

Document the fact that von Mises distribution is not designed
to work as a fully-fledged distribution on a segment of a real line.
TST: clean up Burkardt expm matrix tests
ENH: define a vonmises_line as proper distribution on [-pi, pi]

(yes, this undoes the previous commit, as discussed in the PR)
BUG: fix moments for invgamma

n-th moment only exists for n < a.
TST: mark the ncf normalization test as a knownfail
MAINT: use explicit formulas for invgamma stats
TST: remove redundant code