Follow code conventions on ActiveRecord tests

[guilleiguaran]

Following with #503 (by @smartinez87), I changed "something=>other" to "something => other" on ActiveRecord tests

[guilleiguaran]

Also I notice that there are some tests using Model.find(:all) and Model.find(:first) instead of Model.all and Model.first, these must be changed?

[brajadorable]

Have you seen the comment on #503 ??

Also here #498

[josevalim]

Exactly, thanks for the pull request but such changes just break old patches and pull requests while there is no explicit benefit in merging them.

[guilleiguaran]

@brajadorable @josevalim. I haven't read the comments and you are right. Thanks!!