Decommission the support for Java 6

It's going to the end of lifecycle, also it caused too many issues in
Travis CI build caused by "SunCertPathBuilderException: unable to find
valid certification path to requested target".

.travis.yml

@@ -2,8 +2,8 @@ language: java
 jdk:
   - oraclejdk7
   - oraclejdk8
-  - openjdk6
   - openjdk7
+  - openjdk8
 before_install:
   - chmod +x gradlew
   #

build.gradle

@@ -155,12 +155,24 @@ task javadocJar(type: Jar, dependsOn:javadoc) {
 task checkVersionNumbersInReadme << {
     def readme = file("readme.md")
     def looksLikeVersionNumber = ~/\d+\.\d+\.\d+/
-    def versionNumbersInReadmeFile = readme.readLines().collectMany { line ->
-        looksLikeVersionNumber.matcher(line).collect { match ->
-            (toolkitVersion == match) ? null : match
-        }.findResults{ x -> x }
+    def textNeedFixedVersion = 'Since version 3.7.6 the toolkit no longer support Java SE 6.'
+
+    def versionNumbersInReadmeFile = readme.readLines()
+        .findAll { line ->
+            !line.startsWith(textNeedFixedVersion)
+        }
+        .collectMany { line ->
+            looksLikeVersionNumber.matcher(line).collect { match ->
+                (toolkitVersion == match) ? null : match
+            }.findResults{ x -> x }
+        }
+
+    def decommissionJava6LineWithFixedVersion = readme.readLines().find {line ->
+        line.startsWith(textNeedFixedVersion)
     }
+
     assert versionNumbersInReadmeFile.isEmpty()
+    assert decommissionJava6LineWithFixedVersion != null
 }
 
 artifacts {

readme.md

@@ -8,7 +8,7 @@ For more information, please read [Installation and Setup](#installation-and-set
 
 ## Building
 
-To build the ari-toolkit, you must have the Java Development Kit (JDK) v6.0 or above installed. The project can be built with the command `gradlew build`.
+To build the ari-toolkit, you must have the Java Development Kit (JDK) v7.0 or above installed. The project can be built with the command `gradlew build`.
 
 
 ## Introduction
@@ -84,9 +84,11 @@ The javadoc is available online: [Toolkit javadoc](http://ausregistry.github.com
 
 The following environment specifics are required:
 
-#### Java 6
+#### Java Support
 
-The Toolkit has been developed against the standard Java 6 API, and has no runtime dependencies on external libraries.
+The Toolkit has been developed against the standard Java API, and has no runtime dependencies on external libraries.
+
+Since version 3.7.6 the toolkit no longer support Java SE 6. Only Java SE 7 and above are supported. 
 
 #### UTF-8 Encoding