Snapshot Failure Reporting Shows Line Number inside snapshot and not test

[jacobgardner]

When there's a snapshot failure, it reports the assertion occurred outside of the test and inside of the snapshot lib module.

Diff < left / right > :
<"This is a test for \nmultiline strings"
>"This is a test for \nmultiline stringz"

', src\lib.rs:103:17

It would probably be more useful if this showed inside of the test itself instead.