RUBY-741: Change pool_size to max_pool_size option, lazy instantiate connections
RUBY-741: Allow min_pool_size to be provided
RUBY-741: Allow maxPoolSize and minPoolSize in URI
RUBY-811: Default database to admin if none provided
Merge pull request #542 from mongodb/RUBY-811

RUBY-811: Default database to admin if none provided
Merge pull request #541 from mongodb/RUBY-741

RUBY-741: Support minPoolSize and maxPoolSize
Send messages separately if using gle
RUBY-787 Add in specific errors to bulk write classes
RUBY-787 Add in errors for invalid update, replacement docs and selector
Check for errors to determine if document was inserted instead of ok value