Grammar in assertion messages is not valid English.

[denbeigh2000]

Example: Failed: Expected <method> to be called 1 time but was called 0 times on <object> with any args, but was not.

Let's do something slightly more grammatically valid that is easy to generate from our existing functions.

Possibly something like: Failed: Expected <method> to be called 1 time instead of 0 times on <object> with any args, but was not.

[denbeigh2000]

github is hard. Use #112