This is MakerLabBoard core source files, make Arduino IDE supports STM32F103XX cortex-m3 arm cpu.

中文详细教程:http://makerlab.me/guides/2

You must use 1.5.8 Beta. http://arduino.cc/en/Main/Software

You can use git or zip(https://github.com/MakerLabMe/MakerLabBoard/archive/master.zip). Then put the folder in the Arduino IDE hardware/arduino directory.Like this:

Mac: right click the Arduino.app --> "Show Package Contents" and go to Contents/Resources/Java/hardware/arduino and copy the core files to there.

Like this:

hardware/arduino > ls    
avr	sam	stm32
#The folder name must be **stm32**,because I hardcoded the folder name.
hardware/arduino > cd stm32
hardware/arduino/stm32 > ls
firmwares	programmers.txt	system
boards.txt	libraries	readme.md	variants
cores		platform.txt	sloadhost

Now restart the Arduino IDE, you can see the Tools>Board will add MakerLab Board. Then you can use Arduino IDE for stm32f103 based board.

more info.