Add a raw flag to the completed command

[dwainm]

Fixes #182

This command outputs the raw markdown one can see when editing a task.

To test:

1. Create a task that has some markdown in it. Example:

[markdown link](https://github.com/)

2. Mark that task as completed.

3. From the project root run go run . sync

4. From the project root run go run . cl and notice that you'll only see markdown link

5. From the project root run go run . cl --raw and notice the markdown shows, exposing the link to github.com.

[dwainm]

@sachaos thinking about this more, would this work, and if so, should the flag be --raw or --no-format or --raw-md

[sachaos]

@dwainm I think --raw is OK.

[kenliu]

I'll review this issue over the next few days.

[kenliu]

Hi @dwainm i'm not sure why, but when I checked out this PR and ran sync I consistently get this error message (403). Once I switch back to master it seems to work fine.

todoist on  dwainm/master:master [?] via 🐹 v1.20.1 
➜ ./todoist sync    
Error: bad request: 403 Forbidden

[kenliu]

hi @dwainm I think this PR needs to be rebased against master to verify that it is working (and there are conflicts right now). If it's okay with you I think (?) I can push to your PR but since your PR is on the master branch of your fork (instead of a branch off of master) that will change the state of your fork. Just a heads up in case I decide to do this.