MongoDB Ruby Driver v0.20

If upgrading from a previous version of the Ruby driver, please read these notes carefully,
along with the 0.20_UPGRADE doc.

• Support for new commands:
  • Collection#find_and_modify
  • Collection#stats
  • DB#stats
• Query :fields options allows for values of 0 to exclude fields (houdini, railsjedi).
• GridFS
  • Option to delete old versions of GridFileSystem entries.
  • Filename is now optional for Grid#put.
  • Option to write arbitrary attributes to a file: @grid.put(@DaTa, :favorite_phrase => "blimey!")
  • Indexes created on the chunks collection are now unique. If you have an existing chunks collection,
    you may want to remove
• Removed the following deprecated items:
  • GridStore class
  • RegexpOfHolding class
  • Paired connections must now be initialized with Connection.paired
• BSON-related code extracted into two separate gems: bson and bson_ext (thx to Chuck Remes).
  • mongo_ext no longer exists.
  • BSON::Binary constructor can now take a string, which will be packed into an array.
  • Exception class adjustments:
    • Mongo::InvalidObjectID moved to BSON::InvalidObjectID
    • Mongo::InvalidDocument moved to BSON::InvalidDocument
    • Mongo::InvalidStringEncoding moved to BSON::InvalidStringEncoding
    • Mongo::InvalidName replaced by Mongo::InvalidNSName and BSON::InvalidKeyName
  • BSON types are now namespaced under the BSON module. These types include:
    • Binary
    • ObjectID
    • Code
    • DBRef
    • MinKey and MaxKey
  • Extensions compile on Rubinius (Chuck Remes).