Consider using Ruby v1.9 hash syntax in Hash#mocha_inspect

[floehopper]

We're still using the hash rocket style here whereas we've already changed the code and the documentation.

Are there any reasons not to make this change? Perhaps it makes the distinction between a keyword-style hash and a normal hash less clear...?

[floehopper]

It looks as if we fixed this for Ruby keyword arguments in #652. Perhaps we can use the same code for a non-keyword argument Hash...?

[floehopper]

In #588 I had some concerns about the only distinction between a standard Hash and a keyword argument Hash being the wrapping braces. However, I'm now convinced that this is OK.