Problems in README, project needs a different name

Problem one:

> First up add Javro to your existing JSON Schema project.
> 
> `npm install --save-dev javro`

...this installs a different `javro`: https://www.npmjs.com/package/javro

Problem two:

```js
const { jvro, SchemaRegistryAvroFetcher } = require('javro');
```
(just a minor typo... `jvro` should be `javro`)