[FIX] compiler: escape backticks in attributes

Before this commit, the generated code crashed if an attribute in
the template contained backticks. The compiler output something
like

```js
   let block1 = createBlock(`<div foo="`bar`"/>`);
```

The backticks are now properly escaped.

src/compiler/code_generator.ts

@@ -282,6 +282,7 @@ export class CodeGenerator {
       for (let block of this.blocks) {
         if (block.dom) {
           let xmlString = block.asXmlString();
+          xmlString = xmlString.replace(/`/g, "\\`");
           if (block.dynamicTagName) {
             xmlString = xmlString.replace(/^<\w+/, `<\${tag || '${block.dom.nodeName}'}`);
             xmlString = xmlString.replace(/\w+>$/, `\${tag || '${block.dom.nodeName}'}>`);