Honor lib64 libdir path

Some systems set libdir as /lib64, thus we need to handle it properly.

CMake 3.0 provides GNUInstallDir module, but since that feature is too new I just did a trivial hack here.
Merge pull request #11 from cicku/patch-2

Honor lib64 libdir path for cmake.
Fixed a segfault that could happen if the Widgets are destroyed after the Gui. fixes #12
Update Authors and Chnagelog for 0.1.2.
Initialise the CMake LIB_SUFFIX var.
Merge branch 'master' into pychan_port