Add "replaceAll" function and documentation

This commit adds a `replaceAll` function which takes three arguments - an
original string, the substring to replace, and the string with which to
replace it. This is of particular use when generating node names from IP
addresses where the node name may not contain "." characters.

README.md

@@ -46,6 +46,7 @@ Gomplate is an alternative that will let you process templates which also includ
 		- [`slice`](#slice)
 		- [`split`](#split)
 		- [`splitN`](#splitn)
+		- [`replaceAll`](#replaceAll)
 		- [`title`](#title)
 		- [`toLower`](#tolower)
 		- [`toUpper`](#toupper)
@@ -355,6 +356,23 @@ $ gomplate -i '{{ range splitN "foo:bar:baz" ":" 2 }}{{.}}{{end}}'
 foo
 bar:baz
 ```
+#### `replaceAll`
+
+Replaces all occurrences of a given string with another.
+
+##### Example
+
+```console
+$ gomplate -i '{{ replaceAll "." "-" "172.21.1.42" }}'
+172-21-1-42
+```
+
+##### Example (with pipeline)
+
+```console
+$ gomplate -i '{{ "172.21.1.42" | replaceAll "." "-" }}'
+172-21-1-42
+```
 
 #### `title`
 

gomplate.go

@@ -4,7 +4,6 @@ import (
 	"io"
 	"log"
 	"net/url"
-
 	"strings"
 	"text/template"
 
@@ -39,6 +38,7 @@ func (g *Gomplate) RunTemplate(text string, out io.Writer) {
 func NewGomplate(data *Data, leftDelim, rightDelim string) *Gomplate {
 	env := &Env{}
 	typeconv := &TypeConv{}
+	stringfunc := &stringFunc{}
 	ec2meta := aws.NewEc2Meta()
 	ec2info := aws.NewEc2Info()
 	return &Gomplate{
@@ -65,6 +65,7 @@ func NewGomplate(data *Data, leftDelim, rightDelim string) *Gomplate {
 			"contains":         strings.Contains,
 			"hasPrefix":        strings.HasPrefix,
 			"hasSuffix":        strings.HasSuffix,
+			"replaceAll":       stringfunc.replaceAll,
 			"split":            strings.Split,
 			"splitN":           strings.SplitN,
 			"title":            strings.Title,

stringfunc.go

@@ -0,0 +1,10 @@
+package main
+
+import "strings"
+
+// stringFunc - string manipulation function wrappers
+type stringFunc struct{}
+
+func (t stringFunc) replaceAll(old, new, s string) string {
+	return strings.Replace(s, old, new, -1)
+}

stringfunc_test.go

@@ -0,0 +1,16 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestReplaceAll(t *testing.T) {
+	sf := &stringFunc{}
+
+	assert.Equal(t, "Replaced",
+		sf.replaceAll("Orig", "Replaced", "Orig"))
+	assert.Equal(t, "ReplacedReplaced",
+		sf.replaceAll("Orig", "Replaced", "OrigOrig"))
+}