added strong, because i needed it :-)

Hey Carl,
please add my pull request with the support for strong self macros :-)

reason a weakself inside a block can become nil after the first usage,
so we need strongself, if we like to execute more than two thins on self

details here:
http://albertodebortoli.github.io/blog/2013/08/03/objective-c-blocks-caveat/
http://dhoerl.wordpress.com/2013/04/23/i-finally-figured-out-weakself-and-strongself/