Docs: Quaternion desc clean up.

docs/api/en/math/Quaternion.html

@@ -11,8 +11,8 @@
 		<h1>[name]</h1>
 
 		<p class="desc">
-			Implementation of a [link:http://en.wikipedia.org/wiki/Quaternion quaternion].
-			This is used for [link:https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation rotating things].
+			Implementation of a [link:http://en.wikipedia.org/wiki/Quaternion quaternion].<br/>
+			Quaternions are used in three.js to represent [link:https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation rotations].
 		</p>
 
 

docs/api/zh/math/Quaternion.html

@@ -11,8 +11,8 @@
 		<h1>[name]</h1>
 
 		<p class="desc">
-			Implementation of a [link:http://en.wikipedia.org/wiki/Quaternion quaternion].
-			This is used for [link:https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation rotating things].
+			Implementation of a [link:http://en.wikipedia.org/wiki/Quaternion quaternion].<br/>
+			Quaternions are used in three.js to represent [link:https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation rotations].
 		</p>