Fat arrow hash syntax is better on some occasions

we may have a preference for using the newer
hash syntax, and i use it on most occasions.
however, we must not have the build failing
for something that the language supports and
we don't prefer.

some good use cases for the fat arrow hash
just for enhanced readability, because it
can represent a flow or connection, are:

1. state machine transitions:

```transition :ready => :published```
reads better than
```transition ready: :published```

2. specifying joins in arel:

```joins(:document => :document_sources)```
reads better than
```joins(document: :document_sources)```

also, i personally don't prefer seeing
both hash syntaxes used on the same line,
which this test forces me to write:

```joins(document_sources: :document)
     .where({'documents.id' => document.id})```