Normalized Ruby style.

I went over the source code and normalized the style. Hopefully, this will make it easier for others to dig into Resque's code-base.

* `alias` does not need Symbols.
* Prefer `alias` to `alias_method` when aliasing previously defined methods.
* Use less explicit `return`s.
* Keep code within 80 columns.
* Add white-space around important statements or blocks of code.
* Removed trailing white-space.
* Avoid using the ternary operator with densely packed code.
* Break densely packed lines into multiple lines.
* Use parentheses for all method call, except ones used as declarative statements.
* Avoid single-letter variable names.

Tests pass on:

* Ruby 1.9.3-p194.
* Rubinius 2.0.0 (1.8 mode obviously)

Feel free to also adjust style where needed.