Revert "consider these as binary, so git will not alter line-endings"

This reverts commit 8f3aa220dbab931bfd5a32bdb7d7e77c785c1796.

We will find a better fix for #116. In the meantime, we want to see
diffs for changes to test-data.
diff --git a/test/data/.gitattributes b/test/data/.gitattributes
deleted file mode 100644
index 87e56e7..0000000
--- a/test/data/.gitattributes
+++ /dev/null
@@ -1 +0,0 @@
-/*	binary