Extract tool info into new class, self-update command works now only for PHAR version

It is another approach for #710 - make self-update command works only for PHAR version, great idea by @tucksaun !
It will no mislead users for command which is sometimes available and sometimes missing.

// cc @tucksaun @GrahamCampbell @Seldaek 
IMO not. This proposal was done in #710 .

Below my opinion:

> If one run self-update command on non-phar version he should get info that this action is allowed only with phar version.
> Otherwise one who read README file and want to simply run `self-update` as described will get no command found.