Document capabilities and limitations of current implementation

[fizruk]

For now, odin is able to detect a subclass of fragile decorated object problem (EO version of fragile base class problem). However, this is not properly documented in the project. This has to be fixed.

[Leosimetti]

Here is the first draft of the documentation.

[nikololiahim]

Should be (for now) resolved in #24.

[fizruk]

@Leosimetti please update documentation, including unjustified assumptions defect and general description and limitations (as in #17 and #18)

[Leosimetti]

@fizruk see #45