added AngularAcceleration

[dunmatt]

No description provided.

[iliekturtles]

• Essentially same review as angular velocity. Squash commits / change message to be in imperative: "Add AngularAcceleration."
• Changes in diff below. Removal of first assert_eq recommended but not required.

diff --git a/src/si/angular_acceleration.rs b/src/si/angular_acceleration.rs
index a953fe7..47dbd95 100644
--- a/src/si/angular_acceleration.rs
+++ b/src/si/angular_acceleration.rs
@@ -1,9 +1,9 @@
-//! Angular Acceleration (base unit radian per second squared, s⁻²).
+//! Angular acceleration (base unit radian per second squared, s⁻²).

 quantity! {
     /// Angular acceleration (base unit radian per second squared, s⁻²).
     quantity: AngularAcceleration; "angular acceleration";
-    /// Dimension of angular acceleration (base unit radian per second squared, s⁻²).
+    /// Dimension of angular acceleration, T⁻² (base unit radian per second squared, s⁻²).
     dimension: ISQ<
         Z0,     // length
         Z0,     // mass
@@ -26,8 +26,7 @@ quantity! {
 mod tests {
     storage_types! {
         use ::lib::f64::consts::PI;
-        use num::One;
-        use num_traits::FromPrimitive;
+        use num::{FromPrimitive, One};
         use si::angle as a;
         use si::angular_acceleration as aa;
         use si::quantities::*;
@@ -36,20 +35,12 @@ mod tests {

         #[test]
         fn check_units() {
-            Test::assert_eq(
-                &AngularAcceleration::new::<aa::radian_per_second_squared>(
-                    V::from_f64(2.0 * PI).unwrap()
-                ),
-                &AngularAcceleration::new::<aa::degree_per_second_squared>(
-                    V::from_f64(360.0).unwrap()
-                )
-            );
-
             test::<a::radian, t::second, aa::radian_per_second_squared>();
             test::<a::degree, t::second, aa::degree_per_second_squared>();

             fn test<A: a::Conversion<V>, T: t::Conversion<V>, R: aa::Conversion<V>>() {
                 let square_second = Time::new::<T>(V::one()) * Time::new::<T>(V::one());
+
                 Test::assert_approx_eq(&AngularAcceleration::new::<R>(V::one()),
                     &(Angle::new::<A>(V::one()) / square_second).into());
             }

[iliekturtles]

Manually merged. Thanks again for the PR!