RUBY-807 Bump max wire version for 2.8 features
Merge pull request #521 from estolfo/RUBY-807-wire-version

RUBY-807 Bump max wire version for 2.8 features
RUBY-735 Fail with descriptive error when attempting to authenticate with bad mechanism
Merge pull request #522 from estolfo/RUBY-735-auth-mech-error

RUBY-735 Fail with descriptive error when attempting to authenticate with bad auth mech
RUBY-806 Use listIndexes command with wire version >= 3
RUBY-806 Use MONGODB_2_8 wire version constant