Upgrade atlassian-connect-express

If you are creating a new atlassian-connect-express (ACE) add-on, then all you need to do is follow the instructions in the readme of ACE.

If you have an existing Connect add-on using ACE 0.8.x, follow these steps to update.

1. Change the version of atlassian-connect-express to ~0.9.0 in package.json
2. Rename atlassian-plugin.xml to atlassian-connect.json per our migration guide Specific notes relating to ACE:
   • You must have the lifecycle installed event registered to /installed
   • Update routes/index.js to return atlassian-connect.json instead of the xml descriptor
   • Apart from the {{localBaseUrl}} variable, atlassian-connect.json no longer supports substitution from config.json. Any substituted variables will need to be directly placed into your descriptor.
3. The function addon.httpClient() now returns a promise to the outgoing request, rather than the request directly. By the time the promise is resolved the request is not writeable, so you must pass in any parameters as part of the first argument to get(), post() etc.
   
   Additionally, we no longer support passing the method type by the 'method' parameter, instead you must call the appropriate function on the httpClient. For example, code should be migrated from

    addon.httpClient(req)({
        method: 'POST',
        uri: '/some/url',
        json: data,
        userKey: userKey
    })

   to:

    addon.httpClient(req).post({
        uri: '/some/url',
        json: data,
        userKey: userKey
    });

   Note, that httpClient options take a userKey object, rather than the username.
4. Run npm install
5. Test with node app.js