Update rebasing/fetching in protocol guide

Functional changes:

* Don't forget to fetch before rebasing.
* Change Thin recommendation to Unicorn.
* Remove `--rebase` due to discussion
  [here](https://github.com/thoughtbot/dotfiles/pull/111).

Improvements for better readability/documentation:

* Replace `<>` style code comments with sentence instructions.
* Use full options flags (`--verbose`, `--delete`, etc.) for clarity.
* Use `<branch-name>` consistently (angle brackets and `-name` suffix).
Improve explanations in Trello guide

Based on feedback from @jessieay and @adarshp.
Apply Sandi Metz Rails guidelines

http://gist.io/4567190
Apply Sandi Metz testing guidelines

http://gist.io/4567190
Add the "convince your pair" high-level guideline

http://gist.io/4567190
Five line methods, 100 lines objects
Link to Metz’ slide on assertions about state
Use `self` only for class methods and assignments
Organize route-based guidelines in thier own section

* Adds a "Rails Routes" section
* Moves route-related guidelines from "Rails" to "Rails Routes"
Use `not_to` instead of `to_not`.

* Do not split infinitives.
Use RSpec's expect syntax

The reasons to do so include:

* Style: it highlights the verification phase of the Four-Phase Test
  well by starting each line with `expect`, wrapping the outcome in the
  parentheses.
* Consistency across RSpec specs.
* Consistency with Jasmine.
* Avoids weird, confusing errors when testing delegate/proxy objects.
* Avoids Ruby warning with `should ==`.
Use present? and blank? in conditionals

Using `present?` or `blank?` in conditionals has several benefits:

1. Allows for the use of Null Objects
2. Makes it easier to keep conditionals positive, avoiding `unless`
3. Clarifies the intention of the conditional
Move present/blank to appropriate section
Revert "Move present/blank to appropriate section"

This reverts commit 2bee9e8ac8dc4354cd54a578c74d7ff5f7b93353.

Revert "Use present? and blank? in conditionals"

This reverts commit 1541baa6cbccf0b9f2291fbe8091bda70e003ab3.

There is a lot of discussion still happening in #99 - it's clear that I
prematurely merged that pull request.
Wrap existing lines at 80 chars
Reformat links in lists to use reference style

* Prevents wrapping long list items, improving readability
* Removes the need for short URLs
Add rule avoid `any_instance` in RSpec.

* `any_instance` promotes depending on concretions.
* `any_instance` hides complexity.
* Pure stubs promotes isolation and dependency injection.
* Using dependency injection promotes inversion of control.
Add more indepth style for Sass
Move Trello guide into Playbook

A more recent version of this guide has been moved and edited in the
playbook:

https://github.com/thoughtbot/playbook/blob/master/book/one-weeks-iteration.md

Rather than maintain two versions and potentially cause confusion about
where to look for the process, I think we should stick to just the
playbook version.
make it more clear what do do instead of protected