Ignore unnecessary classes (text-lg and leading-7)

## Feature Request

It would be nice if it could ignore unnecessary classes.

An example:
```
.text-lg {
    font-size: 1.125rem;
    line-height: 1.75rem;
}
```

Currently converts to:
```
.text-lg {
  @apply text-lg leading-7;
}
```

But it should be just:
```
.text-lg {
  @apply text-lg;
}
```

Since `text-lg` comes with `line-height: 1.75rem`