Don't upset different Swift compilers

Version 0.8.0 makes pre- and post-Swift-5.0 compilers play along nicely. There were compilation issues downstream revolving around Double.scaled(from:toExponential:).

Furthermore, the usage of BinaryInteger.isDivisible(by:) is deprecated as of Swift 5.0, because there is now a BinaryInteger.isMultiple(of:) built into the Standard Library.

Update Hashable conformance

Use hash(into:) for Rational: Hashable conformance (#34)

* Use hash(into:) for Rational: Hashable conformance

* Refine doc comment

Swift 5

Update for Swift 5 (#32)

* Update dependencies to Swift 5

* Update Travis

* Update Structure version

Update powersOfTwo API

0.6.0

Refine power of two (#31)

@inlinable

Merge pull request #30 from dn-m/inlinable

Add @inlinable to various operations

Prevent Rational Explosion

Merge pull request #28 from dn-m/negate-rational

Fix Rational negate bug

Refine quadratic implementation

Merge pull request #25 from dn-m/quadratic

Refine quadratic(_:_:_:) implementation

Add Linux Support

Merge pull request #24 from dn-m/linux

Add support for Linux

Power to the Public

Make Power(Generator|Sequence) public.

Swift 4.2

Merge pull request #6 from dn-m/swift-4.2

Update for Swift 4.2