Fix bug in decodeJson() function (amphp#113)

Merge pull request amphp#105 from dickson-michael/master

Add support to Protocol::AuthSwitchResponse

Fix code style

Fix ignored port in getConnectionString() (amphp#93)

Interpret a filesystem path host as an unix domain socket

Add test for INSERT … SELECT

Test for amphp#89.

Fix ConnectionConfig key map

The key map was not being used prior.