Remove 'postinstall' script from package.json.

[Álvaro Brey]

This has already been reported in the main tui.image-editor repo: nhn/tui.image-editor#286. However, this repo (the vue wrapper) also has that script: (https://github.com/nhn/toast-ui.vue-image-editor/blob/master/package.json#L14)

In order to fix this, and allow people with Yarn (such as me!) to use the vue wrapper, you should:

• Update the tui-image-editor version in dependencies
• Remove the postinstall script
• Make a release

[김진우]

Updated to v1.2.0