[Typo] In the maven docs: chd -> cdh

Author: Andrew Or <andrewor14@gmail.com>

Closes #548 from andrewor14/doc-typo and squashes the following commits:

3eaf4c4 [Andrew Or] chd -> cdh

docs/building-with-maven.md

@@ -45,7 +45,7 @@ For Apache Hadoop 2.x, 0.23.x, Cloudera CDH MRv2, and other Hadoop versions with
     $ mvn -Pyarn-alpha -Dhadoop.version=2.0.5-alpha -Dyarn.version=2.0.5-alpha -DskipTests clean package
 
     # Cloudera CDH 4.2.0 with MapReduce v2
-    $ mvn -Pyarn-alpha -Dhadoop.version=2.0.0-cdh4.2.0 -Dyarn.version=2.0.0-chd4.2.0 -DskipTests clean package
+    $ mvn -Pyarn-alpha -Dhadoop.version=2.0.0-cdh4.2.0 -Dyarn.version=2.0.0-cdh4.2.0 -DskipTests clean package
 
     # Apache Hadoop 2.2.X ( e.g. 2.2.0 as below ) and newer
     $ mvn -Pyarn -Dhadoop.version=2.2.0 -Dyarn.version=2.2.0 -DskipTests clean package