CRC example for SD driver

Revision:
0:e60fda833675
diff -r 000000000000 -r e60fda833675 .gitignore
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/.gitignore	Mon Dec 18 22:58:44 2017 +0000
@@ -0,0 +1,4 @@
+.build
+.mbed
+projectfiles
+*.py*