attempt to fix jdk6/7 appveyor config

appveyor.yml

@@ -10,7 +10,9 @@ skip_tags: true
 environment:
   matrix:
     - JAVA_HOME: C:\Program Files\Java\jdk1.6.0
+      M2_HOME: C:\bin\apache-maven-3.2.5
     - JAVA_HOME: C:\Program Files\Java\jdk1.7.0
+      MAVEN_OPTS: -Dhttps.protocols=TLSv1,TLSv1.1,TLSv1.2
     - JAVA_HOME: C:\Program Files\Java\jdk1.8.0
 
 matrix:
@@ -20,17 +22,19 @@ matrix:
 
 # install required tools (maven, secure-file, encrypted files)
 install:
+  - cmd: if not exist "C:\bin\apache-maven-3.2.5\bin\*.*" cinst maven --version 3.2.5 --allow-empty-checksums
   - cmd: echo %JAVA_HOME%
   - cmd: echo %M2_HOME%
 
 # build and install artifacts
 build_script:
-  - mvn clean install -DskipTests
+  - '"%M2_HOME%\bin\mvn" clean install -DskipTests'
 
 # verify artifacts
 test_script:
-  - mvn test
+  - '"%M2_HOME%\bin\mvn" test'
 
 # preserve dependencies between builds
 cache:
   - C:\Users\appveyor\.m2
+  - C:\bin\apache-maven-3.2.5