Fix format string warning in -[JMStaticContentTableViewSection description]

This fixes the following warning:

> `JMStaticContentTableViewController/JMStaticContentTableViewSection.m:134:46: Values of type 'NSInteger' should not be used as format arguments; add an explicit cast to 'long' instead`

when building for 64-bit platforms.
Merge pull request #11 from cdzombak/master

Fix format string warning in -[JMStaticContentTableViewSection description]