Support {:else} blocks in @first, @last

[claviska]

Simple PR to add support for {:else} in @first and @last helpers, per linkedin/dustjs#720.

• Passes all tests locally: 575 tests, 837 assertions, 0 failures, 0 skipped
• Docs still need to be updated (is there a place to submit PRs for documentation?)

[claviska]

Not sure why the Travis build is failing, but the error seems unrelated. Any ideas?

[sethkinast]

For style purposes, could you follow the pattern in the filter function with skip and nonternary return values?

[sethkinast]

The helpers build uses loose versioning for the Jasmine dep and it's changed out from under you, not your fault. Would you mind adding a test?

Once this is merged you can open a PR against the gh-pages branch of the main Dust repo for the docs.

Thanks a bunch for the PR!

[claviska]

Thanks. The format is consistent now and I added two tests. They're my first unit tests so feel free to suggest changes. 🙃

[sethkinast]

Looks great!

[sethkinast]

Nice, thanks for taking the time to send a PR! :)

[sethkinast]

@jimmyhchan #138 will fix the test failures, I'll try to work on it soon...