json-cpp Code

Fixed continuous integration matrix for debug/release build. Made static debug build verbose.

Added continuous integration matrix for debug/release build. Made static debug build verbose.

Added continuous integration matrix for shared/static library (specified through environment variables).

Added continuous integration failure e-mail notification.

Added clang compiler for continuous integration.

Added basic Travis CI integration contributed by Igor Okulist.

Fixed CMake / Unix build instructions.

- New CMake based build system. Based in part on contribution from
Igor Okulist and Damien Buhl (Patch #14). Added support for running
tests and building with DLL on Windows.
- added missing JSON_API
- Visual Studio DLL: suppressed warning "C4251: <data member>: <type>
needs to have dll-interface to be used by..." via pragma push/pop
in json-cpp headers.
- New header json/version.h now contains version number macros
(JSONCPP_VERSION_MAJOR, JSONCPP_VERSION_MINOR, JSONCPP_VERSION_PATCH
and JSONCPP_VERSION_HEXA). While this header is generated by CMake,
it is committed to ease build with alternate build system
(CMake only update the file when it changes avoid issues with VCS).

- Patch #3393345: BOOST_FOREACH compatibility. Made Json::iterator more standard compliant, added missing iterator_category and value_type typedefs (contribued by Robert A. Iannucci).
- Patch #3474563: added missing JSON_API on some classes causing link issues when building as a dynamic library on Windows (contributed by Francis Bolduc).