doc: start go1.5.txt

Change-Id: I0f9cf081cb280f0a805ee7f5178a5cbed0d4ad88
Reviewed-on: https://go-review.googlesource.com/1842
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/doc/go1.5.txt b/doc/go1.5.txt
new file mode 100644
index 0000000..a80f253
--- /dev/null
+++ b/doc/go1.5.txt
@@ -0,0 +1 @@
+crypto/tls: change default minimum version to TLS 1.0. (https://golang.org/cl/1791)