Allow & anywhere in selector

This is to support things like

(.foo
  (.bar &
    :color blue))

which would have previously been rendered

.foo {
  .bar & {
    color: blue;
  }
}

because it was only looking for an & at the beginning of the
selector.

src/ast/selector.ts

@@ -14,8 +14,8 @@ export class Selector {
     return Array.prototype.concat(
       ...this.parents.map((parent) => {
         return parent.getLineages().map((lineage) => {
-          if (this.name.value.match(/^&/)) {
-            return lineage + this.name.value.slice(1);
+          if (this.name.value.match(/&/)) {
+            return this.name.value.replace('&', lineage);
           }
           return lineage + ' ' + this.name.value;
         });

src/tests/compiler.test.ts

@@ -202,3 +202,9 @@ test('compiles nested mixins', (t) => {
   `);
   t.equal(result, '.container{margin-top:50px;margin-bottom:50px;margin-left:100px;margin-right:100px;}');
 });
+
+test('respects ampersand even if it\'s not the first element of the selector', (t) => {
+  t.plan(1);
+  const result = compile(`(.foo (.bar & :color blue))`);
+  t.equal(result, '.bar .foo{color:blue;}');
+});