updated maven pom for Java8
updated maven pom for Java8

todoooo/gson,DanySK/gson-extras,todoooo/gson,mbrukman/gson,testcenter/gson,testcenter/gson,mbrukman/gson,gv2011/jsoncore,DanySK/gson-extras,todoooo/gson,testcenter/gson,google/gson,DanySK/gson-extras,mbrukman/gson