content/versioning-proposal: fix year of gophercon discussion

The versioning discussions happened at Gophercon 2016, not 2015.

Change-Id: I80236f9f364f080daf0e46a487cab92e71a18a0c
Reviewed-on: https://go-review.googlesource.com/109655
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/content/versioning-proposal.article b/content/versioning-proposal.article
index f6dd1d6..0b95a77 100644
--- a/content/versioning-proposal.article
+++ b/content/versioning-proposal.article
@@ -18,10 +18,10 @@
 and we encouraged people to create one.
 The Go community created many tools with different approaches.
 Each one helped us all better understand the problem,
-but by mid-2015 it was clear that there were now too many solutions.
+but by mid-2016 it was clear that there were now too many solutions.
 We needed to adopt a single, official tool.
 
-After a community discussion started at GopherCon in July 2015 and continuing into the fall,
+After a community discussion started at GopherCon in July 2016 and continuing into the fall,
 we all believed the answer would be to follow the package versioning approach
 exemplified by Rust’s Cargo, with tagged semantic versions,
 a manifest, a lock file, and a