Allow to_output to accept multiple arguments

[malclocke]

Hi folks,

Would you be willing to accept a PR that allows the following?

expect { some_method }.to_output(/This stuff/, /and this stuff/).to_stdout

As to_output currently only accepts one argument, the only solution I can see is to do the following:

expect { some_method }.to_output(/This stuff/).to_stdout
expect { some_method }.to_output(/and this stuff/).to_stdout

and this is less than ideal when some_method is expensive.

[myronmarston]

This is already supported by passing a compound matcher:

expect { some_method }.to_output(
  a_string_matching(/This stuff/).and matching(/and this stuff/
).to_stdout