Added squashing docs

docs/SQUASHING.md

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+# How do I "squash" my commits?
+
+Before you start, [make sure your text editor is associated with Git](https://help.github.com/articles/associating-text-editors-with-git/) to not close without a response, otherwise you'll see some weird behavior.
+
+Then update your refs to be sure you have the latest code:
+
+```shell
+ git fetch --all
+```
+
+## Rebase
+
+Rather than merge develop into your branch, we prefer to rebase off of develop. Depending on how you are working with the repo, this step may be different.
+
+If you are working from a forked copy on a branch other than develop (i.e. you created a feature branch) run:
+
+```shell
+git rebase -i develop
+```
+
+If you are working from a forked copy on the develop branch run:
+
+```shell
+git rebase -i HEAD~X
+```
+With `X` being the number of commits you have added.
+
+If you are working from the main repo run:
+
+```shell
+git rebase -i origin/develop
+```
+
+This says to rebase your work onto develop.
+
+## Squash
+
+From here, you'll see something like:
+
+```
+pick f48d47c The first commit I did
+pick fd4e046 The second commit I did
+```
+
+You'll want to change everything after your first commit from `pick` to `squash`. This tells git you want to squash these commits into the first one.
+
+From here, you'll get an editor that will let you change the commit messages.
+
+```
+# This is a combination of 2 commits.
+# The first commit's message is:
+The first commit I did
+
+# This is the 2nd commit message:
+
+The second commit I did
+```
+
+You'll want to remove or comment out everything except for the first message, which you can edit to be a more complete summary of your changes.
+
+To finish, you'll force push this new commit with the following command:
+
+```shell
+git push origin [my-feature-branch] --force-with-lease
+```
+
+The `--force-with-lease` flag will refuse to update a branch if someone else has updated it upstream, making your force push a little safer.