Refactor: Consolidate conditional helpers

[erikjung]

Closes #3

Summary

• The ifAnd and ifOr helpers have been replaced with leaner, renamed and and or helpers.
• The ifElse helper has been removed.
• A new compare helper has been added.

This new compare helper is modeled after the (identically named) helper found at https://github.com/assemble/handlebars-helpers/blob/master/lib/helpers/helpers-comparisons.js, and differs by using functions from the Ramda.js library. Why? In addition to reducing a bit of code on our end, I think there are (and will be) other opportunities to leverage the functional nature of Ramda (opposed to something like Underscore) in other helper functions.

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CC @saralohr @nicolemors

[tylersticka]

Heh, now that I'm reading this, I guess && and || really aren't comparisons.

Assemble just keeps those as their own little helpers. Maybe they are unique, and I conflated them with ifEqual because of the similarity in naming convention.

[erikjung]

@tylersticka I'd be fine with either of these scenarios:

• We add back ifAnd and ifOr (perhaps naming them differently...I feel that anything with "if" should also have an "unless" counterpart)
• We add another helper (let's call if logic for now) that acts like compare but supports the && and || operators.

[tylersticka]

I like the first idea better but by a small margin. I'd be find with ifAnd and ifOr or even just and and or. (That's a confusing sentence.)

[erikjung]

@tylersticka Changes made, and PR description updated.

[tylersticka]

Yay! :clap: