Implement standard rule layout

[plaird]

We started this rule back in the days of Bazel 0.5.2 and have kept the same layout since. We need to reorganize the rule to adhere to the standard layout:

https://docs.bazel.build/versions/master/skylark/deploying.html#repository-content

[plaird]

This work will also require a rename of the Git repository from bazel-springboot-rule to rules-spring

[plaird]

I think we should also be looking at bzl_library during this work.

https://github.com/bazelbuild/bazel-skylib/blob/master/bzl_library.bzl

This might be required to support stardoc #28 ?

[plaird]

The repackaging work (aside from the repo rename) has been completed an is in the repackaging_v2.0 branch. I will publish a new release from this branch. It has been tested internally at Salesforce. The top-level README will be updated with the migration details.

• I will rename the repo after further testing, to ensure that GitHub will properly redirect requests from the old repo to the new repo name.
• I will merge the 2.0 branch into master soon.

[plaird]

The repo rename happened in #97 and the docs have been updated. I think we are done!

Now that we are in proper attire, I just sent a PR to finally get us added to AwesomeBazel: jin/awesome-bazel#94