Add new slide with all overloadable operators

Added new slide with further information on which operators can be
predefined. Also corrected the outdated list with instance methods of the
Enumerable class (now they are 48; +lazy).
Add new slides with all overloadable operators

Added new slides in lecture 5  with further information on which operators can be
predefined.

Also corrected the outdated list with instance methods of the Enumerable class (now they are 48; +lazy). (again in lecture 5)
Merge branch 'add-slides-05' of https://github.com/yasen23/ruby-lectures into add-slides-05

Conflicts:
	lectures/05-classes-objects-enumerable.slim