Add link to exception causes document

README.md

@@ -7,6 +7,8 @@ A combination of a C# server and an arduino program that allows the control of a
  	- Andrew C, Karen van Eck, Mike C
 
 ## Useful Links
+### For another blog post
+ - [Arduino error codes](https://github.com/esp8266/Arduino/blob/master/doc/exception_causes.md)
 ### For Multicast networkinterface blog post
  - [NetworkInterface class](https://msdn.microsoft.com/en-us/library/system.net.networkinformation.networkinterface(v=vs.110).aspx))
  - [Sockoverflow answer](http://stackoverflow.com/questions/2192548/specifying-what-network-interface-an-udp-multicast-should-go-to-in-net)