Upgraded OmniFocus to 2.0.1

[crainiarc]

Update OmniFocus to 2.0.1
Add shasum for integrity check

[nanoxd]

@crainiarc I'm still able to get the latest version by going to the old url. This new version restricts us to manual changes for the url. @rolandwalker I know you wanted to get every cask versioned. Would you like to start doing so?

[crainiarc]

Figured that having a checksum to verify the versions would be a better option. What do you think?

[rolandwalker]

@nanoxd , per #1021 (comment), I do want to go that direction.

But, I'm in no hurry to change the Casks because, as outlined in that comment and some other places, I don't yet have backend code in place which gives users a tangible benefit for versioning.

It also seems that, given discussions in #1021 and elsewhere, not all the maintainers may agree with moving toward versioning in any case. If/when we do make such a switch, I want there to be good consensus behind it, not have it be the decision of one person.

[nanoxd]

@rolandwalker I agree with the change if there is a way to facilitate upgrades 😄. For the time being, I believe that casks are better as latest due to the emphasis on allowing new users get the latest file without the need to check if the cask was updated.

[rolandwalker]

@crainiarc thanks for the patch.

For the time being, we can leave this file unchanged for the reasons @nanoxd gave above. Over upcoming months, I plan to move in the direction of your suggestion, per the roadmap for brew cask upgrade #4678.