Detect I2C devices

Revision:
0:81685bb49271
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/.gitignore	Mon Apr 23 09:25:26 2018 +0000
@@ -0,0 +1,4 @@
+.build
+.mbed
+projectfiles
+*.py*