- updated documentation wrt. new repository layout
- temporarily switched off Homebrew --HEAD building (can only be switched on after release)
- set copyright date to 2018

fix cmake install directory (for real this time)

* Rename 'develop' folder to 'include/nlohmann'
* Rename 'src' folder to 'single_include/nlohmann'
* Use <nlohmann/*> headers in sources and tests
* Change amalgamate config file

Templatize std::string in binary_reader #941

Allow overriding THROW/CATCH/TRY macros with no-exceptions #938

Removed compiler warning about unused variable 'kMinExp'

Howto installation of json_fwd.hpp (fixes #923)

- Builds and runs test cases from individual sources rather than from amalgamation.
- Checks whether amalgamation would create the same single-header file as checked in.

Also fixed some warnings from GCC.