Attempt to fix links from doc/index.md

The current master branches do no longer reflect the directory layout at
the time of writing. Let's point to the latest revision at the time of
creating this doc.

This includes making the links proper Markdown URL links as a drive-by
change.

doc/index.md

@@ -10,9 +10,9 @@ Serial ports are some of the oldest external interfaces exposed by system kernel
 
 ## References
 
- * https://github.com/pyserial/pyserial/blob/master/serial/serialposix.py#L354
- * https://github.com/Fazecast/jSerialComm/blob/master/src/main/c/OSX/SerialPort_OSX.c#L241
- * https://github.com/node-serialport/node-serialport/blob/master/src/serialport_unix.cpp#L137
- * https://github.com/jacobsa/go-serial/blob/master/serial/open_darwin.go#L239
- * https://github.com/nyholku/purejavacomm/blob/master/src/jtermios/macosx/JTermiosImpl.java#L434
- * https://github.com/npat-efault/picocom/blob/master/termios2.txt
+ * <https://github.com/pyserial/pyserial/blob/master/serial/serialposix.py#L354>
+ * <https://github.com/Fazecast/jSerialComm/blob/v2.0.2/src/main/c/OSX/SerialPort_OSX.c#L241>
+ * <https://github.com/node-serialport/node-serialport/blob/a31078f054f23c47e9de7cc8b1c7e79d6e4e6c0c/src/serialport_unix.cpp#L137>
+ * <https://github.com/jacobsa/go-serial/blob/master/serial/open_darwin.go#L239>
+ * <https://github.com/nyholku/purejavacomm/blob/master/src/jtermios/macosx/JTermiosImpl.java#L434>
+ * <https://github.com/npat-efault/picocom/blob/master/termios2.txt>