-Wconversion
-Wconversion

* https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html
* http://programmers.stackexchange.com/questions/122608/clang-warning-flags-for-objective-c-development/124574#124574

In clang: `-Wconversion` implies `-Wshorten-64-to-32`

Streamlet/GoogleHelper,Streamlet/GoogleHelper,Streamlet/GoogleHelper,Streamlet/GoogleHelper,Streamlet/GoogleHelper