Generate API docs from source code comments (#2491)

* Generate api docs from source code

* Add a bunch of doxygen comments

* more doxygen comments

* Add the in-progress api docs

* script to generate docs from travis

* Add doc generation to the travis job

* make travis_docs.sh commit the work it does

* make sure the docs script exits cleanly

tmk_core/common/led.h

@@ -19,6 +19,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #define LED_H
 #include "stdint.h"
 
+/* FIXME: Add doxygen comments here. */
 
 /* keyboard LEDs */
 #define USB_LED_NUM_LOCK                0
@@ -40,4 +41,4 @@ void led_init_ports(void);
 }
 #endif
 
-#endif
+#endif