Removed rt linking on OS X. Fixes #24.

CMakeLists.txt

@@ -11,13 +11,13 @@ if(UNIX AND NOT APPLE)
         INCLUDE_DIRS include
         DEPENDS rt pthread
     )
-else ()
+else()
     # Otherwise normal call
     catkin_package(
         LIBRARIES ${PROJECT_NAME}
         INCLUDE_DIRS include
     )
-endif ()
+endif()
 
 ## Sources
 set(serial_SRCS
@@ -25,7 +25,7 @@ set(serial_SRCS
     # include/serial/serial.h
     # include/serial/v8stdint.h
 )
-if (UNIX)
+if(UNIX)
     # If unix
     list (APPEND serial_SRCS src/impl/unix.cc)
 else()
@@ -34,10 +34,8 @@ else()
 endif()
 
 ## Add serial library
-add_library(${PROJECT_NAME}
-    ${serial_SRCS}
-)
-if (UNIX)
+add_library(${PROJECT_NAME} ${serial_SRCS})
+if(UNIX AND NOT APPLE)
     target_link_libraries(${PROJECT_NAME} rt)
 endif()