Include CMake specific files in release tarballs

Fixes #147.
Merge branch '2.5'
Merge
Merge branch '2.5'
github_commits.c: GitHub API v3 requires a User-Agent header
Merge branch '2.5'
Check for key == NULL in json_object_get and json_object_del
Merge pull request #151 from nmlgc/master

Check for key == NULL in json_object_get and json_object_del
Fix CMake build flags for MinGW
Added CMake config files.

This will simplify linking against the lib, both from the build-tree and
install-tree from other CMake projects.

CMakes find_package command uses these configs to locate the exported
targets for the library.

* Also changed so that all CMake options for the project are prepended
  with JANSSON_ so that there is no ambiguity when including this as a
  subdirectory in another CMake project.
Renamed config.h -> jansson_private_config.h

This is because it's really easy to get a name collission if compiling
Jansson as a subproject in a larger CMake project. If one project includes
several subprojects each having their own config.h, this will cause the
wrong file to be loaded.
Merge pull request #157 from JoakimSoderberg/cmake_config_new

Cmake config
Update copyrights for 2014
Make sure the private config is included.
Merge pull request #159 from JoakimSoderberg/config_fix

Make sure the private config is included.
Add CMake build to Travis config.
Fix so that valgrind checks actually works with CMake.

The valgrind tests where not run on the suites.

And valgrind was always returning 0 so set an explicit exit code on exit. I also had forgotten to change the name of TEST_WITH_VALGRIND to JANSSON_TEST_WITH_VALGRIND so that the tests would never use valgrind.
Merge pull request #160 from JoakimSoderberg/cmake_memcheck_fix

Fix so that valgrind checks actually works with CMake.
Merge pull request #161 from JoakimSoderberg/cmake_travis

Add CMake build to Travis config.