Merge pull request #72 from chen3feng/develop

Add Date class
Merge pull request #73 from chen3feng/develop

Add Bitmap and BloomFilter and adjust hash interface
Merge pull request #74 from chen3feng/develop

Fix style
Merge pull request #75 from chen3feng/develop

Fix test
Merge remote-tracking branch 'chen3feng/master'
add varint encoding
make functions as static functions of Varint
implement compression
refactor code following chen3feng's comments
remove Varint from function names
fix comments of chen3feng
add TOFT_ prefix
fix comments of chen3feng
remove private
Merge branch 'master' of https://github.com/yeshunping/toft into yeshunping-master