Auto merge of #199 - nical:mod-exports, r=kvark

Re-export all euclid types and hide the module hierarchy.

There was a mix between things that were reexported in lib.rs (most types) all of which were also accessible through their modules (you get to choose between euclid::Bar and euclid::foo::Bar), and a few that were public but only accessible in sub modules.
Let's clean this up and export everything public in lib.rs. A nice side effect of this is that it makes it possible to export the function euclid::rect which was otherwise clashing with the module euclid::rect.

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src/lib.rs

@@ -72,33 +72,33 @@ pub use scale_factor::ScaleFactor;
 pub use transform2d::{Transform2D, TypedTransform2D};
 pub use transform3d::{Transform3D, TypedTransform3D};
 pub use point::{
-    Point2D, TypedPoint2D,
-    Point3D, TypedPoint3D,
+    Point2D, TypedPoint2D, point2,
+    Point3D, TypedPoint3D, point3,
 };
 pub use vector::{
-    Vector2D, TypedVector2D,
-    Vector3D, TypedVector3D,
+    Vector2D, TypedVector2D, vec2,
+    Vector3D, TypedVector3D, vec3,
 };
 
-pub use rect::{Rect, TypedRect};
+pub use rect::{Rect, TypedRect, rect};
 pub use side_offsets::{SideOffsets2D, TypedSideOffsets2D};
 #[cfg(feature = "unstable")] pub use side_offsets::SideOffsets2DSimdI32;
-pub use size::{Size2D, TypedSize2D};
+pub use size::{Size2D, TypedSize2D, size2};
 
 pub mod approxeq;
-pub mod length;
+pub mod num;
+mod length;
 #[macro_use]
 mod macros;
-pub mod transform2d;
-pub mod transform3d;
-pub mod num;
-pub mod point;
-pub mod rect;
-pub mod scale_factor;
-pub mod side_offsets;
-pub mod size;
-pub mod trig;
-pub mod vector;
+mod transform2d;
+mod transform3d;
+mod point;
+mod rect;
+mod scale_factor;
+mod side_offsets;
+mod size;
+mod trig;
+mod vector;
 
 /// The default unit.
 #[derive(Clone, Copy)]

src/scale_factor.rs

@@ -26,8 +26,8 @@ use std::marker::PhantomData;
 /// may be types without values, such as empty enums.  For example:
 ///
 /// ```rust
-/// use euclid::scale_factor::ScaleFactor;
-/// use euclid::length::Length;
+/// use euclid::ScaleFactor;
+/// use euclid::Length;
 /// enum Mm {};
 /// enum Inch {};
 ///