Fix #3

Apparently, CMake versions < 2.8 expect the FILES keyword in the
file(INSTALL) command.

postinstall.cmake.in

 endif()
 
 if(INIT_FLAVOR AND NOT EXISTS "$ENV{DESTDIR}/etc/default/@PROJECT_NAME@")
-	file(INSTALL "@CMAKE_CURRENT_SOURCE_DIR@/@PROJECT_NAME@.default" DESTINATION "/etc/default" RENAME "@PROJECT_NAME@")
+	file(INSTALL FILES "@CMAKE_CURRENT_SOURCE_DIR@/@PROJECT_NAME@.default" DESTINATION "/etc/default" RENAME "@PROJECT_NAME@")
 endif()
 
 if(INIT_FLAVOR STREQUAL "sysv")
-	file(INSTALL "@CMAKE_CURRENT_BINARY_DIR@/@PROJECT_NAME@.init" TYPE PROGRAM DESTINATION "/etc/init.d" RENAME "@PROJECT_NAME@")
+	file(INSTALL FILES "@CMAKE_CURRENT_BINARY_DIR@/@PROJECT_NAME@.init" TYPE PROGRAM DESTINATION "/etc/init.d" RENAME "@PROJECT_NAME@")
 	if(INSSERV)
 		execute_process(
 			COMMAND ${INSSERV} -p "$ENV{DESTDIR}/etc/init.d" @PROJECT_NAME@
 		)
 	endif()
 elseif(INIT_FLAVOR STREQUAL "upstart")
-	file(INSTALL "@CMAKE_CURRENT_BINARY_DIR@/@PROJECT_NAME@.upstart" DESTINATION "/etc/init" RENAME "@PROJECT_NAME@.conf")
+	file(INSTALL FILES "@CMAKE_CURRENT_BINARY_DIR@/@PROJECT_NAME@.upstart" DESTINATION "/etc/init" RENAME "@PROJECT_NAME@.conf")
 endif()
 
 if(GENERATE_SRS_SECRET AND DD AND BASE64 AND EXISTS "/dev/urandom" AND NOT EXISTS "$ENV{DESTDIR}/etc/${SECRET_FILE}")
 		ERROR_QUIET
 		OUTPUT_STRIP_TRAILING_WHITESPACE
 	)
-file(INSTALL "@CMAKE_CURRENT_BINARY_DIR@/${SECRET_FILE}" DESTINATION "/etc" FILE_PERMISSIONS OWNER_READ OWNER_WRITE)
+file(INSTALL FILES "@CMAKE_CURRENT_BINARY_DIR@/${SECRET_FILE}" DESTINATION "/etc" FILE_PERMISSIONS OWNER_READ OWNER_WRITE)
 file(REMOVE "@CMAKE_CURRENT_BINARY_DIR@/${SECRET_FILE}")
 endif()