Determine how to upgrade between versions.

[cball]

2 proposed ways to attack this:

1. Create a demo repo. Every time we release a new version of bison, we regenerate the app and create a tag. This tag should match the current version of Bison at the time of creation. If we save the version of Bison that was used to generate, we can create a link in the CLI to the git diff. This should give users a step-by-step way to upgrade and is similar to how react-native-upgrade-helper works.
2. Create a bison package that manages the dependencies, write codemods using jscodeshift to patch files appropriately. This is likely the future solution that we could move to once things have stabilized. It does require some dev work to implement properly.

[cball]

Demo repo is here: https://github.com/echobind/bisonapp-versions

Part 2 can be a future enhancement. After #89 is complete, we can add a simple package to manage dependencies and determine the version of Bison that users used initially. This will allow us to generate a diff link using the tags in https://github.com/echobind/bisonapp-versions as the source of truth.

[cball]

Example diff on demo repo: echobind/bisonapp-versions@v1.7.3...v1.7.4

[cball]

With #95, our short term solution will be to have folks manually generate a link to bisonapp-versions based on the version of Bison in their package.json file.

We'll followup with a new package after #89 is done.

[cball]

Newly generated Bison projects should have version information in the package.json file. In the short term, users can use this version to construct a manual diff.

As a followup, we can add a simple script that generates the link for them until #89 is finished.