Add pluralize template func

Fixes #1438

docs/content/meta/release-notes.md

@@ -14,6 +14,7 @@ weight: 10
 * We now use a custom-built `LazyFileReader` for reading file contents, which means we don't read media files in `/content` into memory anymore -- and file reading is now performed in parallel on multicore PCs. [1181](https://github.com/spf13/hugo/issues/1181)
 * Hugo is now built with `Go 1.5` which, among many other improvements, have fixed the last known data race in Hugo. [917] (https://github.com/spf13/hugo/issues/917)
 * Lots of fixes and improvements in the template funcs:
+	* The new `pluralize` template func.  
 	* The `sort` template func now accepts field/key chaining arguments and pointer values. [1330](https://github.com/spf13/hugo/issues/1330)
 	* Several fixes for `slicestr` and `substr`, most importantly, they now have full `utf-8`-support. [1190](https://github.com/spf13/hugo/issues/1190) [1333](https://github.com/spf13/hugo/issues/1333) [1347](https://github.com/spf13/hugo/issues/1347) 
 	*  The new `last` template function allows the user to select the last `N` items of a slice. [1148](https://github.com/spf13/hugo/issues/1148)

docs/content/templates/functions.md

@@ -1,4 +1,4 @@
----
+g---
 aliases:
 - /layout/functions/
 date: 2013-07-01
@@ -366,6 +366,10 @@ Runs the string through the Markdown processesor. The result will be declared as
 
 e.g. `{{ .Title | markdownify }}`
 
+### pluralize
+Pluralize the given word with a set of common English pluralization rules.
+
+e.g. `{{ "cat" | pluralize }}` → "cats"
 
 ### replace
 Replaces all occurrences of the search string with the replacement string.

tpl/template_funcs.go

@@ -14,6 +14,7 @@
 package tpl
 
 import (
+	"bitbucket.org/pkg/inflect"
 	"bytes"
 	"errors"
 	"fmt"
@@ -1371,6 +1372,13 @@ func init() {
 		"readDir":     ReadDir,
 		"seq":         helpers.Seq,
 		"getenv":      func(varName string) string { return os.Getenv(varName) },
+		"pluralize": func(in interface{}) (string, error) {
+			word, err := cast.ToStringE(in)
+			if err != nil {
+				return "", err
+			}
+			return inflect.Pluralize(word), nil
+		},
 	}
 
 }