Add recommended jdk versions

Author: Xylus

doc/installation.md

@@ -14,8 +14,8 @@ To try out a simple quickstart project, please refer to the [quick-start guide](
 	2. Create HBase Schemas - feed `/scripts/hbase-create.hbase` to hbase shell.
 2. Build Pinpoint (Only required if you're building from source)
 	1. Clone Pinpoint - `git clone $PINPOINT_GIT_REPOSITORY`
-	2. Set JAVA_6_HOME environment variable to JDK 6 home directory.
-	3. Set JAVA_7_HOME environment variable to JDK 7+ home directory.
+	2. Set JAVA_6_HOME environment variable to JDK 6 home directory (1.6.0_45 recommended).
+	3. Set JAVA_7_HOME environment variable to JDK 7 home directory (1.7.0_80 recommended).
 	4. Set JAVA_8_HOME environment variable to JDK 8 home directory.
 	5. Run `mvn install -Dmaven.test.skip=true` in Pinpoint home directory.
 3. Pinpoint Collector ([details](#pinpoint-collector))
@@ -67,8 +67,8 @@ There are two options:
 	* JDK 6 installed
 	* JDK 7+ installed
 	* Maven 3.2.x+ installed
-	* JAVA_6_HOME environment variable set to JDK 6 home directory.
-	* JAVA_7_HOME environment variable set to JDK 7+ home directory.
+	* JAVA_6_HOME environment variable set to JDK 6 home directory (1.6.0_45 recommended).
+	* JAVA_7_HOME environment variable set to JDK 7 home directory (1.7.0_80 recommended).
 	* JAVA_8_HOME environment variable set to JDK 8 home directory.
 
 	JDK 7+ and JAVA_7_HOME, JAVA_8_HOME environment variable are required to build **profiler-optional**. For more information about the optional package, please take a look [here](../profiler-optional/README.md).