[CALCITE-541] Update maven-source-plugin to 2.4 to get speedup in jdk 1.8
[CALCITE-541] Update maven-source-plugin to 2.4 to get speedup in jdk 1.8

Old version of maven-source-plugin has "is java.version==1.7" guard check for the usage of 1.7+ features.
New version has proper java.version>=1.7, so it is faster in 1.8

Fixes #35

xhoong/incubator-calcite,datametica/calcite,adeshr/incubator-calcite,hsuanyi/incubator-calcite,vlsi/calcite,minji-kim/calcite,joshelser/calcite-avatica,b-slim/calcite,jcamachor/calcite,julianhyde/calcite,looker-open-source/calcite,glimpseio/incubator-calcite,apache/calcite-avatica,apache/calcite,datametica/calcite,sudheeshkatkam/incubator-calcite,looker-open-source/calcite,hsuanyi/incubator-calcite,julianhyde/calcite,jcamachor/calcite,googleinterns/calcite,datametica/calcite,arina-ielchiieva/calcite,minji-kim/calcite,googleinterns/calcite,googleinterns/calcite,looker-open-source/calcite-avatica,hsuanyi/incubator-calcite,wanglan/calcite,arina-ielchiieva/calcite,adeshr/incubator-calcite,glimpseio/incubator-calcite,amoghmargoor/incubator-calcite,amoghmargoor/incubator-calcite,looker-open-source/calcite-avatica,joshelser/incubator-calcite,jcamachor/calcite,julianhyde/calcite,xhoong/incubator-calcite,minji-kim/calcite,YrAuYong/incubator-calcite,datametica/calcite,b-slim/calcite,mapr/incubator-calcite,julianhyde/calcite,apache/calcite-avatica,dindin5258/calcite,amoghmargoor/incubator-calcite,datametica/calcite,looker-open-source/calcite,yeongwei/incubator-calcite,YrAuYong/incubator-calcite,b-slim/calcite,dindin5258/calcite,xhoong/incubator-calcite,sudheeshkatkam/incubator-calcite,apache/calcite-avatica,vlsi/calcite,apache/calcite-avatica,wanglan/calcite,b-slim/calcite,glimpseio/incubator-calcite,vlsi/incubator-calcite,joshelser/calcite-avatica,apache/calcite,jcamachor/calcite,adeshr/incubator-calcite,sudheeshkatkam/incubator-calcite,glimpseio/incubator-calcite,jcamachor/calcite,minji-kim/calcite,devth/calcite,jcamachor/calcite,devth/calcite,joshelser/incubator-calcite,dindin5258/calcite,vlsi/incubator-calcite,vlsi/calcite,b-slim/calcite,xhoong/incubator-calcite,dindin5258/calcite,sreev/incubator-calcite,datametica/calcite,julianhyde/calcite,YrAuYong/incubator-calcite,looker-open-source/calcite-avatica,arina-ielchiieva/calcite,googleinterns/calcite,sudheeshkatkam/incubator-calcite,apache/calcite,joshelser/calcite-avatica,yeongwei/incubator-calcite,yeongwei/incubator-calcite,looker-open-source/calcite,joshelser/incubator-calcite,hsuanyi/incubator-calcite,googleinterns/calcite,minji-kim/calcite,julianhyde/calcite,wanglan/calcite,apache/calcite,adeshr/incubator-calcite,looker-open-source/calcite-avatica,sreev/incubator-calcite,YrAuYong/incubator-calcite,joshelser/incubator-calcite,mapr/incubator-calcite,apache/calcite,apache/calcite-avatica,sreev/incubator-calcite,looker-open-source/calcite-avatica,dindin5258/calcite,vlsi/calcite,arina-ielchiieva/calcite,looker-open-source/calcite,googleinterns/calcite,looker-open-source/calcite,arina-ielchiieva/calcite,apache/calcite,vlsi/calcite,yeongwei/incubator-calcite,vlsi/calcite,amoghmargoor/incubator-calcite,wanglan/calcite,dindin5258/calcite,sreev/incubator-calcite