added usage of removeFile to example

[yfxie]

related issue: #28

[greggilbert]

Couple of recommendations on this:

1. Squash the commits (git rebase) - it's cleaner
2. Something like this to also remove the file from vue-clip's files prop:

    removeFile(file) {
      this.$refs.vc.removeFile(file);
      var index = this.$refs.vc.files.indexOf(file);
      this.$refs.vc.files.splice(index, 1);
    }