fix(Shadows): Fix incorrect shadow level
fix(Shadows): Fix incorrect shadow level

Remove an incorrect shdaow value and add the new value "24". This might slighly
affect a bit the UI since shadow 4 go from value 6 to 8, 5: 6->16 and 6: 16->24.

Fixes #314

tleunen/react-mdl,tleunen/react-mdl