Use readline in console when supported

$this->stdin->read(); will use readline if the system is detected to
support it.  In linux, you will be able to use the left and right arrow
keys to edit the current line, use the up and down keys to navigate
history, press ^U to delete the entire line, etc.

Before this, using arrow keys in linux will just spam characters like
^[[C^[[A^[[D^[[C^[[A^.  Useful for "Console/cake console"
Correct style
ConsoleInput::_canReadLine change from private -> protected
Merge pull request #1594 from mreishus/feature-readline-support

Use readline in console when supported