provide `between` (or `in_range`) matcher

it'd be nice if there were a matcher to say that a number must be within a specific range, i.e. $x \in [a, b]$.

this is mainly a convenience function as it can also be achieved like this: `expect_that!(x, some(all!(ge(a), le(b))));`

open point: should it be inclusive on both ends ($x \in [a, b]$) or exclusive ($x \in ]a, b[$)? my vote would be for inclusive; alternatively it could take a boolean parameter to specify this? if someone wants one end open and another closed they can always do it manually as per the current manual workaround.