dropped GCC 4.8 support (due to #110)

README.md

@@ -42,7 +42,7 @@ to the files you want to use JSON objects. That's it. Do not forget to set the n
 
 Though it's 2015 already, the support for C++11 is still a bit sparse. Currently, the following compilers are known to work:
 
-- GCC 4.8 - 5.2
+- GCC 4.9 - 5.2
 - Clang 3.4 - 3.7
 - Microsoft Visual C++ 14.0 RC