Changes:

• mysql_common was updated:
  • codec replaced by mysql_common codec;
  • compression support was introduced (see docs on OptsBuilder::compression);
• falure was replaced by thiserror (by @udoprog in #78);
• #79 was fixed;
• #82 was fixed by @tomhoule;
• #57 fixed:
  • PoolOptions structure was introduced;
  • inactive_connection_ttl and ttl_check_interval options were introduced.