Fix trivial spelling mistake (#57)

diff --git a/cmp/compare_test.go b/cmp/compare_test.go
index dc247ca..00b4ccf 100644
--- a/cmp/compare_test.go
+++ b/cmp/compare_test.go
@@ -1849,7 +1849,7 @@
 		var p ts.Poison
 		p.SetPoisonType(5)
 		p.SetExpiration(now)
-		p.SetManufactuer("acme")
+		p.SetManufacturer("acme")
 
 		var hq ts.Headquarter
 		hq.SetID(5)
@@ -1893,9 +1893,9 @@
 			var p1, p2 ts.Poison
 			p1.SetPoisonType(1)
 			p1.SetExpiration(now)
-			p1.SetManufactuer("acme")
+			p1.SetManufacturer("acme")
 			p2.SetPoisonType(2)
-			p2.SetManufactuer("acme2")
+			p2.SetManufacturer("acme2")
 			d.SetPoisons([]*ts.Poison{&p1, &p2})
 			return d
 		}(),
@@ -1920,7 +1920,7 @@
 	-: testprotos.PoisonType(1)
 	+: testprotos.PoisonType(5)
 {teststructs.Cartel}.poisons[1->?]:
-	-: &teststructs.Poison{poisonType: testprotos.PoisonType(2), manufactuer: "acme2"}
+	-: &teststructs.Poison{poisonType: testprotos.PoisonType(2), manufacturer: "acme2"}
 	+: <non-existent>`,
 	}}
 }
diff --git a/cmp/internal/teststructs/project4.go b/cmp/internal/teststructs/project4.go
index 9b50d73..49920f2 100644
--- a/cmp/internal/teststructs/project4.go
+++ b/cmp/internal/teststructs/project4.go
@@ -51,7 +51,7 @@
 func equalPoison(x, y Poison) bool {
 	return x.PoisonType() == y.PoisonType() &&
 		x.Expiration().Equal(y.Expiration()) &&
-		x.Manufactuer() == y.Manufactuer() &&
+		x.Manufacturer() == y.Manufacturer() &&
 		x.Potency() == y.Potency()
 }
 */
@@ -125,18 +125,18 @@
 func (hq *Headquarter) SetCreationTime(x time.Time)       { hq.creationTime = x }
 
 type Poison struct {
-	poisonType  pb.PoisonType
-	expiration  time.Time
-	manufactuer string
-	potency     int
+	poisonType   pb.PoisonType
+	expiration   time.Time
+	manufacturer string
+	potency      int
 }
 
 func (p Poison) PoisonType() pb.PoisonType { return p.poisonType }
 func (p Poison) Expiration() time.Time     { return p.expiration }
-func (p Poison) Manufactuer() string       { return p.manufactuer }
+func (p Poison) Manufacturer() string      { return p.manufacturer }
 func (p Poison) Potency() int              { return p.potency }
 
 func (p *Poison) SetPoisonType(x pb.PoisonType) { p.poisonType = x }
 func (p *Poison) SetExpiration(x time.Time)     { p.expiration = x }
-func (p *Poison) SetManufactuer(x string)       { p.manufactuer = x }
+func (p *Poison) SetManufacturer(x string)      { p.manufacturer = x }
 func (p *Poison) SetPotency(x int)              { p.potency = x }