tried my hand at some better syntax. not so sure about this one :)
Comments and minor cleanup for DDG::Goodie::ABC.
Improved readability a bit for DDG::Goodie::ABC.  Added more tests.
Improved comments in DDG::Goodie::ABC.  Added a complimentary test.
Add pick as a trigger word for DDG::Goodie::ABC. +tests.
Added 'select' as a trigger word.  +refactor, +tests
Very minor updates to comments in DDG::Goodie::ABC
Added a test which fails atm for DDG::Goodie::ABC.
Handle queries like 'choose pick or axe'
Fixed up PR 325 and re-submitting
Merge remote-tracking branch 'origin/master' into pr/325-fix-and-resubmit

Conflicts:
	lib/DDG/Goodie/DuckDuckGo.pm
DDG::Goodie::ABC - Removed @TRIGGERS var and added an attribution.
DuckDuckGo: Add the `use` statement at the top.
DuckDuckGo: Remove the "-" in "t-shirt".

Perl thinks that "t" is a bareword.
DuckDuckGo: Continuation of #363.

Pros:
- No more problems with *_html such as https://duckduckgo.com/?q=duckduckgo+help_html.

Cons:
- No plain text version (only affects the API so it's not that big of a deal).
- Triggers with "duckduckgo" and "ddg" only so "zeroclickinfo" on its own won't trigger.
DuckDuckGo: Update tests.
SumOfNaturalNumbers: Simplify the triggering.
SumOfNaturalNumbers: Faster computation.

- Don't use List::Util for computing the number.
- Stricter regexp.
- Add attribution.
SumOfNaturalNumbers: Add a "from" in the regexp.

So that it can accept "add from 1 to 100"
SumOfNaturalNumbers: Change colon to "is".