calucate the realValue during loading of a block, add skip() and tests
write delta from second value, since the first value is stored in the header of block
create delta binary packing config class
minor
add comment, class header for writer
add comments for fields in writer
refactor writer
comment
fix a bug in test, add random data test
test format
1. verify bytes size generated by writer in UT
2. fix bug of Varint return incorrect size