bugfix: chunkSize in fs.chunks of gridfs should be int32 or int64, not float or double
modify bson.lua
bugfix: int32 for num >= -2^31 and num <= 2^31-1, and int64 for other
bug fix: add a function to handle 'NULL' from cjson
bug fix: add a function to handle 'NULL' from cjson
Merge pull request #1 from fenghui2013/master