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.h

@@ -9,7 +9,7 @@
 #define FMT_GTEST_EXTRA_H_
 
 #include <string>
-#include <gmock/gmock.h>
+#include "gmock.h"
 
 #include "fmt/core.h"
 
@@ -155,7 +155,7 @@ std::string read(fmt::file &f, std::size_t count);
 template <typename Mock>
 struct ScopedMock : testing::StrictMock<Mock> {
   ScopedMock() { Mock::instance = this; }
-  ~ScopedMock() { Mock::instance = 0; }
+  ~ScopedMock() { Mock::instance = nullptr; }
 };
 
 #endif  // FMT_GTEST_EXTRA_H_