Warnings in custom container example of GTKmm Book

[Joaquim Duran <joaquinduran adtelecom es>]

Dear all,

I've executed the custom container example of the Gtkmm Book. When I 
closed the applications the following warnings were displayed:


(lt-example:24330): Gtk-WARNING **: GtkContainerClass::remove not 
implemented for `gtkmm__GtkContainer'

(lt-example:24330): Gtk-WARNING **: GtkContainerClass::remove not 
implemented for `gtkmm__GtkContainer'


This happens with Gtkmm version 2.12.4.


Also, in the documentation web page, there is a small typo in the text 
of the green rectangle:

[...] installed in parallel. *Tthe* gtkmm-2.4 name refers to the [...]

'Tthe' should be corrected to 'The'.

Thanks and Best Regards,
Joaquim Duran