Refactored request options creation

## Review 1
Please review line 88 of OAuth.coffee where there is the comment:
`# This is the only call that replaces placeholders in url`. 
Why are all the other code paths not replacing placeholders in urls?

## Review 2
In OAuth1 the response options where build with the following code:
```coffee
if options.method == 'POST'
	options.form = query
else
	options.qs = query
```
In OAuth2 with this:
```coffee
if options.method == "GET"
	options.qs = query
else
	options.form = query # or .json = qs for json post
```
I implemented this in the new code with the following logic, as per my understanding of RFC, only GET methods can have query strings:
```coffee
form: query if method != 'GET'
qs: query if method == 'GET'
```