Update README.md - unwrap pathComponent

`suggestedFilename` is `String?`
Merge pull request #120 from ricardopereira/patch-1

Update README.md - unwrap pathComponent
Adding documentation
Adding convenience methods for upload and download accepting URLRequestConvertible argument
[Issue #121] URL-encoding application/x-www-form-urlencoded HTTP body
Adding HTTP response validation
- [x]
Adding Alamofire.playground
Improving ParameterEncoding documentation
Adding Advanced Usage section
Whitespace
Adding example usage of URLRequestConvertible
Minor copy editing
Adding section about generic response object serialization
Fixing markup
Copy editing
[Issue #123] Adding link to Git submodule documentation in installation section
Dispatching to custom serial queue for task creation to ensure unique identifiers
Using default session operation queue
Making manager queue private