minor: replacing redcarpet with kramdown to resolve ruby 2.0 install errors
RUBY-650 move check for exhaust option into method
RUBY-650 raise exception for exhaust + limit combo
RUBY-650 be less verbose and improve style
RUBY-657 support URI encoded usernames and passwords
RUBY-658 fixing issue with default db from connection uri
RUBY-659 modify comment to reference handling code
RUBY-650 catch adding multiple options
RUBY-679 raise error if exhaust used with mongos
RUBY-662 prevent ObjectId initialization with bad data
RELEASE 1.9.2
minor: updating copyright information for rebrand
RUBY-661 add support and tests for maxTimeMS
RUBY-661 member? -> include?
RUBY-660 allow aggregation helper to return cursors
RUBY-660 move version test up
minor: update tested versions list and thread-safety info in README
RUBY-661 on 2.5.2+
minor: removing extra ; in collection test
RUBY-686 cleaning up lib structure a bit in prep for auth

* moved: gridfs code into its own folder
* moved: all connection pool related code into its own folder
* moved: all socket and socket utils to connection/socket
* moved: functional modules (read concern, write concern) to functional folder
* fixed: conversion unit test was requiring some specific paths, not needed