Remove Cargo.lock

It has become out of date, and if it's not updated regularly, it becomes
a hindrance rather than a help. Please refer to the following pull
request for a discussion of this issue:
#148

Author: hannobraun

.gitignore

@@ -2,3 +2,4 @@
 *.rs.bk
 *.svd
 target
+Cargo.lock