Release 0.2.2

Casting from floating point to integers now returns None on overflow, avoiding rustc's undefined behavior. This applies to the cast function and the traits NumCast, FromPrimitive, and ToPrimitive.

Contributors: @apopiak, @cuviper, @dbarella

Release 0.2.1

The new FloatCore trait offers a subset of Float for #![no_std] use. This includes everything except the transcendental functions and FMA.
The new Inv trait returns the multiplicative inverse, or reciprocal.
The new Pow trait performs exponentiation, much like the existing pow function, but with generic exponent types.
The new One::is_one method tests if a value equals 1. Implementers should override this method if there's a more efficient way to check for 1, rather than comparing with a temporary one().

Contributors: @clarcharr, @cuviper, @vks

breaking change: There is now a std feature, enabled by default, along with the implication that building without this feature makes this a #![no_std] crate.
- The Float and Real traits are only available when std is enabled.
- Otherwise, the API is unchanged, and num-traits 0.1.43 now re-exports its items from num-traits 0.2 for compatibility (the semver-trick).

Contributors: @cuviper, @termoshtt, @vks

num-traits now has its own source repository at rust-num/num-traits.
ParseFloatError now implements Display.
The new AsPrimitive trait implements generic casting with the as operator.
The new CheckedShl and CheckedShr traits implement generic support for the checked_shl and checked_shr methods on primitive integers.
The new Real trait offers a subset of Float functionality that may be applicable to more types, with a blanket implementation for all existing T: Float types.

Thanks to @cuviper, @Enet4, @fabianschuiki, @svartalf, and @yoanlcq for their contributions!

No prior release notes were kept. Thanks all the same to the many contributors that have made this crate what it is!