README was recently renamed to README.md which broke cmake config. When we run 'cmake .', we get this error:

CMake Error at /usr/share/cmake-2.8/Modules/CPack.cmake:338 (message):
  CPack package description file:
  /home/amberj/projects/opencog/README could not be found.
Call Stack (most recent call first):
  /usr/share/cmake-2.8/Modules/CPack.cmake:342 (cpack_check_file_exists)
  CMakeLists.txt:632 (INCLUDE)

To fix this, I'm editing the CmakeLists.txt so that README is replaced with README.md in cpack config.

Note: I guess we don't need cpack configuration as it is very outdated now. If other devs agree to it, I can send in another pull request later to remove cpack lines from cmake config of opencog.
Merge pull request #92 from amberj/fix-readme-missing-cmake-error

README was recently renamed to README.md which broke 'cmake .'