Add uniq function.

Closes #30

doc.go

@@ -167,6 +167,8 @@ These are used to manipulate lists: '{{ list 1 2 3 | reverse | first }}'
 	- initial: Get all but the last item in a list: 'list 1 2 3 | initial' returns '[1 2]'
 	- append: Add an item to the end of a list: 'append $list 4' adds '4' to the end of '$list'
 	- prepend: Add an item to the beginning of a list: 'prepend $list 4' puts 4 at the beginning of the list.
+	- reverse: Reverse the items in a list.
+	- uniq: Remove duplicates from a list.
 
 Dict Functions:
 

functions.go

@@ -233,6 +233,7 @@ var genericMap = map[string]interface{}{
 	"last":    last,
 	"initial": initial,
 	"reverse": reverse,
+	"uniq":    uniq,
 
 	// Crypto:
 	"genPrivateKey":  generatePrivateKey,

list.go

@@ -78,3 +78,23 @@ func compact(list []interface{}) []interface{} {
 	}
 	return res
 }
+
+func uniq(list []interface{}) []interface{} {
+	dest := []interface{}{}
+
+	skip := func(haystack []interface{}, needle interface{}) bool {
+		for _, h := range haystack {
+			if reflect.DeepEqual(needle, h) {
+				return true
+			}
+		}
+		return false
+	}
+
+	for _, item := range list {
+		if !skip(dest, item) {
+			dest = append(dest, item)
+		}
+	}
+	return dest
+}

list_test.go

@@ -96,3 +96,16 @@ func TestReverse(t *testing.T) {
 		assert.NoError(t, runt(tpl, expect))
 	}
 }
+
+func TestUniq(t *testing.T) {
+	tests := map[string]string{
+		`{{ list 1 2 3 4 | uniq }}`:                   `[1 2 3 4]`,
+		`{{ list "a" "b" "c" "d" | uniq }}`:           `[a b c d]`,
+		`{{ list 1 1 1 1 2 2 2 2 | uniq }}`:           `[1 2]`,
+		`{{ list "foo" 1 1 1 1 "foo" "foo" | uniq }}`: `[foo 1]`,
+		`{{ list | uniq }}`:                           `[]`,
+	}
+	for tpl, expect := range tests {
+		assert.NoError(t, runt(tpl, expect))
+	}
+}