User activity tracking

I think the annotate models gem is adding these newlines each time you run it.  This is "commit noise" and should be avoided.  Either figure out how to prevent annotate models from doing this in the first place or make sure to delete the extra whitespace before you commit.  Also make sure you run this _before_ you add/commit any files:

```
$ git diff
```

I _highly_ recommend you use

```
$ git add -p
```

which will prompt you to add changes one section of changes at a time across all changed files.  This _forces_ you to look at every change individually and ask yourself, "Did I mean to commit this?"  I use `git add -p` all the time.