documenting size_mode in speed dial tutorial

Signed-off-by: Shwetank Dixit <emailshwetank@gmail.com>
minor fixes to language of the size_mode explanation

Signed-off-by: Shwetank Dixit <emailshwetank@gmail.com>
Merge pull request #65 from shwetank/master

adding size_mode info to speed dial tut