update dependencies

vendor/github.com/mgutz/str/doc.go

@@ -0,0 +1,19 @@
+// Package str is a comprehensive set of string functions to build more
+// Go awesomeness. Str complements Go's standard packages and does not duplicate
+// functionality found in `strings` or  `strconv`.
+//
+// Str is based on plain functions instead of object-based methods,
+// consistent with Go standard string packages.
+//
+//      str.Between("<a>foo</a>", "<a>", "</a>") == "foo"
+//
+// Str supports pipelining instead of chaining
+//
+//      s := str.Pipe("\nabcdef\n", Clean, BetweenF("a", "f"), ChompLeftF("bc"))
+//
+// User-defined filters can be added to the pipeline by inserting a function
+// or closure that returns a function with this signature
+//
+//      func(string) string
+//
+package str