Increase surefire heap size

Prevents out of memory errors with many concurrent tests.

pom.xml

@@ -229,7 +229,7 @@
         <configuration>
           <parallel>all</parallel>
           <threadCount>1</threadCount>
-          <argLine>-Xmx256m</argLine>
+          <argLine>-Xmx512m</argLine>
           <redirectTestOutputToFile>true</redirectTestOutputToFile>
           <forkedProcessTimeoutInSeconds>1800</forkedProcessTimeoutInSeconds>
           <runOrder>random</runOrder>