Add more compilers to CI and increase FMT_PEDANTIC warning levels (#736)

* Add a _lot_ more warnings to FMT_PEDANTIC
Fix these warnings

* Add more compilers to CI
Fix (some) of the compiler errors with them

* Enable -Werror on CI
Increase warning level on MSVC when compiling with FMT_PEDANTIC

* Add VS 2013 and 2015 to Appveyor

* Fix Appveyor tests
Formatting

* Implement requested changes
Fix some of the MSVC warnings
Implement C++11 integer_sequence

* Reintroduce appveyor-build.py

* Remove ranges-test from tests

* Remove (some) explicit warning suppressions
Fix C++ standard setting in CI

* Remove (some) explicit warning suppressions
Fix C++ standard setting in CI

* Fix test builds with C++11

* Enable pedantic warnings on tests

* Fix warnings from edits to master

* Cleanups

* Add C++11 support to ranges.h
Re-enable ranges-test
Fix a Visual Studio error about function not returning a value in printf.h
Fix a bug in .travis.yml

test/gtest-extra.cc

@@ -75,7 +75,7 @@ std::string read(file &f, std::size_t count) {
   do {
     n = f.read(&buffer[offset], count - offset);
     // We can't read more than size_t bytes since count has type size_t.
-    offset += static_cast<std::size_t>(n);
+    offset += n;
   } while (offset < count && n != 0);
   buffer.resize(offset);
   return buffer;