add initial cmake script
add helpful error message if gtest isn't set up
Fix cmake build.
undo setup-autotools.sh -> setup-gtest.sh rename, add setup-cmake.sh instead
correct reference to setup-cmake.sh
hyphenate cmake target names
improve cmake build

* Move binaries into the bin directory and libs into the lib directory in the output
* Make sure the actual binary output file of capnp-tool is just capnp
* Remove need for deprecated cmake get_property function
add myself to CONTRIBUTORS
Merge pull request #124 from joshuawarner32/cmake

Add initial cmake build support