Add be_format test matcher

[yanivpr]

Add a test matcher for the format.
Could be useful to test that a conversion has happened.

Usage:

context 'the thumb format' do
  it 'should be JPEG' do
    @uploader.thumb.should be_format('JPEG')
   end
end

[thomasfedb]

@yanivpr does the value of @expected need to be normalised at all? e.g. @expected.downcase?

[yanivpr]

@thomasfedb To clarify - you mean that I should cover all cases?
Something like /\A#{@actual_expected}\z/i.match(@expected)

[thomasfedb]

@yanivpr is a regex the most efficient way to handle that?

[thomasfedb]

Also @yanivpr, it might be worthwhile ensuring that your matcher gets used within the carrierwave test suite.

[yanivpr]

• Test format case insensitive.
• Use format test matcher in the test suite.
• Add format test matcher to readme file.

[thomasfedb]

Can you change 'PNG' to 'png'.

[yanivpr]

👍

[thomasfedb]

This is looking great @yanivpr. If you could address the three comments I've left above, and also squash all your changes into a single commit (how to) then I'll git it merged! 🏆

[yanivpr]

Thank you for the code review!
I have squashed the commits.

[thomasfedb]

Lovely. Cheers @yanivpr.