Fix some errors in phpdocs.

[ci skip]
Add a note about missing break in switch statement.

[ci skip]
Remove erroneous duplication of INFO in Redis profiles.

This oversight didn't end up in a blatant bug only because the correct
handler definition for INFO replaced the old class in the profile.
Fix incorrect usage of instance method in static method.

We also added a test to check that the socket-based connection backend
throws an exception when unable to resolve hostnames.
Add @property-read tags to parameters class.

[ci skip]
Add @property-read tags to client options class.

[ci skip]
Make Pipeline::executeCommand() return $this for fluent interface.
Fix phpdocs for fluent interfaces.

[ci skip]
[tests] No need to reassign $exception.
[tests] Fix a couple of glitches in our base PHPUnit classes.
[test] Fix wrong variable.
Apply more phpdoc fixes.
[tests] Fix a couple of innocuous glitches.
Move @property-read tags for parameters and options to interfaces.

This actually makes sense since whatever the actual implementation is,
classes implementing these interfaces should provide at least those
properties that are actively used through the library.
Run php-cs against test suite.

[ci skip]
[tests] Remove unused "use" directives.
Remove useless return statement.
Explicitly return null value.
Reword paragraph in README about HHVM compatibility.