Inja v2 (#67)

* inja2

* header only

* reduce dependencies

* code cleaning

* c++17

* use stdc++

* code cleaning

* infrastructure

* header only

* add infrastructure

* fix tests

* use minimum clang 6

* code cleaning, polyfill for c++11

* fix some file tests

* fix readme

* update appveyor

* fix polyfill and ci

* fix polyfill

* fix ci?

* test msvc __cplusplus

* add doxygen

* activate all tests

* code cleaning

* add coveralls, set default to dot notation

* add html test

* add doxygen comments

* test single_include file

* change build folder in appveyor

* correct make arguments in appveyor

* fix appveyor arguments

amalgamate/config.json

@@ -1,8 +1,8 @@
 {
 	"project": "inja",
-	"target": "single_include/inja.hpp",
+	"target": "single_include/inja/inja.hpp",
 	"sources": [
-		"../include/inja.hpp"
+		"../include/inja/inja.hpp"
 	],
 	"include_paths": [
 	]