conflict with PID_v1

I've run into a conflict with the PID library

```
~/sketchbook/libraries/MySensors/core/Version.h:9:0: warning: "LIBRARY_VERSION" redefined
 #define LIBRARY_VERSION "2.0.0-beta"
 ^
In file included from incubot.ino:9:0:
~/sketchbook/libraries/PID_v1/PID_v1.h:3:0: note: this is the location of the previous definition
 #define LIBRARY_VERSION 1.1.1
```
