Add #pragma clang diagnostic push to allow generally stricter checks
Mark several const variables only used in their own .m files static
Address stricter compiler warnings by making trivial changes
Fix getter for progress in MRProgressOverlayView
Turn on hard mode

With some minor restrictions.
Fixed unsafe floating-point type comparisons
Removed wrong attribute
Ignore "-Wassign-enum" for `options:0`
Added -Wno-gnu to use MIN, MAX, ABS macros
Fixed `pod lib lint` warnings
Fixed warning because of unused var if NS_BLOCK_ASSERTIONS is enabled

The warning was:
"MRMethodCopier.m:27:10: warning: unused variable 'success' [-Wunused-variable]"
This happens because CocoaPods sets as a default build setting 'NS_BLOCK_ASSERTIONS'.
Fixed .travis.yml
Merge branch 'master' into fix/53_compiler_warnings
Fixed warning from missing cast
Merge pull request #56 from mrackwitz/fix/53_compiler_warnings

Fix #53: Stricter compiler warnings