Build system uses C++17

[mikepyne]

The command in the build system file is:

"cmd": ["g++", "-std=c++1y", "${file}", "-o", "${file_path}/${file_base_name}"]

The std parameter is c++1y. The man page for gcc version 4.8.4 says that c++1y is "the next revision of the ISO C++ standard, tentatively planned for 2017".

There is a specific parameter for C++11 (c++11), which should be used instead.