Update glide.go

Fix a trivial typo in a usage message.

glide.go

diff --git a/glide.go b/glide.go
index 79616b1..d64c4c8 100644
--- a/glide.go
+++ b/glide.go
@@ -186,7 +186,7 @@
 				},
 				cli.BoolFlag{
 					Name:  "insecure",
-					Usage: "Use http:// rather than https:// to retrieve pacakges.",
+					Usage: "Use http:// rather than https:// to retrieve packages.",
 				},
 				cli.BoolFlag{
 					Name:  "no-recursive, quick",