* Fixed and added tests for `quantile' and `median', documented them
* Added `sort-samples', documented it
* Removed `real-quantile' and `real-median' (too many design choices
right now; will revisit when implementing Kernel Density Estimators)
* Documented `absdev' and `absdev/median'
* Fixed `update-statistics*': now uses O(1) space as advertised (if the
sequences of values and weights both use O(1) space)
* Changed types of binning functions: allows using #:key in the future
(when TR supports function type cases that differ only by keyword
argument types better), places optional weights at the end like other
statistics functions
* Clarified binning docs about sort stability and half-open intervals
clean up build
Moved `float-complex?' and `number->float-complex' to `math/base',
documented them
Documented `flexpt1p'
Removed `samples->immutable-hash' (not covariant anyway; not going to
use hashes)
Fixed a few limit cases in some distributions (e.g. (uniform-dist 0 0) didn't
act like a delta distribution, (beta-dist 0 0) and (beta-dist +inf.0 +inf.0)
pretended to be defined by unique limits even though they can't be)
Made integer distributions' pdfs return +nan.0 when given non-integers
Added "private/statistics/counting.rkt", for hashing and binning samples
Added `flvector-sums' (cumulative sums with single rounding error)
Added `flinteger?', `flnan?' and `flrational?', which are faster than their
non-flonum counterparts (at least in Typed Racket; haven't tested untyped)
