Removing jdk 6, adding jdk 8.
Removing jdk 6, adding jdk 8.

gssiyankai/RoaringBitmap,lemire/RoaringBitmap,RoaringBitmap/RoaringBitmap,gssiyankai/RoaringBitmap,lemire/RoaringBitmap,lemire/RoaringBitmap,gssiyankai/RoaringBitmap,RoaringBitmap/RoaringBitmap,okrische/RoaringBitmap,RoaringBitmap/RoaringBitmap,okrische/RoaringBitmap,okrische/RoaringBitmap,lemire/RoaringBitmap,RoaringBitmap/RoaringBitmap