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/ranges-test.cc

@@ -11,7 +11,7 @@
 
 #include "fmt/ranges.h"
 
-#include "gtest/gtest.h"
+#include "gtest.h"
 
 #include <vector>
 #include <array>
@@ -30,7 +30,6 @@ TEST(RangesTest, FormatVector2) {
   EXPECT_EQ("{{1, 2}, {3, 5}, {7, 11}}", ivf);
 }
 
-#if FMT_USE_INTEGER_SEQUENCE
 TEST(RangesTest, FormatMap) {
   std::map<std::string, int32_t> simap{{"one", 1}, {"two", 2}};
   EXPECT_EQ("{(one, 1), (two, 2)}", fmt::format("{}", simap));
@@ -87,4 +86,3 @@ TEST(RangesTest, FormatStruct) {
 
 #endif  // (__cplusplus > 201402L) || (defined(_MSVC_LANG) && _MSVC_LANG >
         // 201402L && _MSC_VER >= 1910)
-#endif  // FMT_USE_INTEGER_SEQUENCE