date_received vs received_at methods on a message

In our current example, we use message.date. Based on our discussions of the spoofability of that, I ran `message.methods`, saw `date_received` at the top, and rewrote the example in my fork to look like this.

```ruby
require 'active_support/all'

account.messages.where(date_before: 3.hours.ago.to_i, date_after: 5.hours.ago.to_i).each do |message|
  puts message.subject
  puts Time.at(message.received_at)   # 2013-07-31 20:33:56 -0500
  puts Time.at(message.date_received) # 2013-07-31 20:33:56 -0500
end
```

But then I noticed that there are two methods, `received_at` and `date_received`, which return the same value in my tests. I have not documented `date_received`, only `received_at`.

Questions:

1. Are these the same and if not, how are they distinct and what's the use case for each?

2. Can you tell me (like I'm 5) how I could have explored these methods more deeply myself before coming to you to ask, so I can do so next time? 

On the documentation specifically, which I'm wanting to pull request on once this is sorted out, here's my reasoning for the changes:

1. Shows the reader Time.at, which tells them that they are getting a utc integer back and if they want it in time, this is how to do it. No running to other docs to figure that out if you don't have it memorized. 

2. Uses `date_received` / `received_at` instead of date, which is default the skimmer of documentation is likely wanting. 

Again this morning contextio is saving me hours and costing me minutes. Thanks Ben!