Update README.md
Improve Composer notes in the readme

`require-dev` is better than `require` for such tool, because it is not
needed to be installed on production.

`composer update` without specifying vendor libraries as an argument
will try to update all dependencies which may not be desired.

Related to: https://github.com/andres-montanez/MagallanesSite/pull/3
Merge pull request #122 from hkdobrev/composer-readme-improvements

Improve Composer notes in the readme
Merge branch 'master' into develop
Add "vendor" to gitignore
Load core classes wit hcomposer autoloader
Load custom tasks and commands by composer autoload mechanism
Remove old Autoload class
Revert "Remove old Autoload class"

This reverts commit 3f3253bbee3493c71e09a3074fd28a9d4485fc6c.
Use default autoloader when composer autoloader has been not initialized