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/compile-test/CMakeLists.txt

@@ -1,10 +1,12 @@
 # Test if compile errors are produced where necessary.
 
-cmake_minimum_required(VERSION 2.8)
+cmake_minimum_required(VERSION 3.1.0)
 
 include(CheckCXXSourceCompiles)
+include(CheckCXXCompilerFlag)
+
 set(CMAKE_REQUIRED_INCLUDES ${CMAKE_CURRENT_SOURCE_DIR}/../../include)
-set(CMAKE_REQUIRED_FLAGS ${CPP14_FLAG})
+set(CMAKE_REQUIRED_FLAGS ${CXX_STANDARD_FLAG} ${PEDANTIC_COMPILE_FLAGS})
 
 function (generate_source result fragment)
   set(${result} "