Set the computed variables as static, per Thomas recommendation. The speed gain is 2% over previous implementation.

Signed-off-by: Stéphane Mons <st.mons.lists@free.fr>
Merge pull request #46 from Smons/master

Modified StringExtension.FormatSize
Merge pull request #27 from macoslib/master

Merge changes
Merge branch 'macoslib-master'