Holiday: Normalize holiday data and query to handle 'day'

[machineloop]

Description of new Instant Answer, or changes

The query "when is thanksgiving" doesn't trigger this IA because the list of Holidays for "Canada" and "USA" (canada.txt, us.txt) have the name of the holiday as "thanksgiving day", so a check for "thanksgiving" does not match.

This PR removes "day" from all holidays, and strips it from the query when present to allow it to match the normalized data.

Related Issues and Discussions

Fixes #3448

People to notify

CC: @sekhavati @moollaza

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IA Page: http://duck.co/ia/view/holiday Maintainer: @sekhavati

[daxtheduck]

Holiday

Description: Gives the next occurrence of the specified holiday. If a year is specified, it will give the event date for the given year.

Example Query: when is halloween, when is christmas day in the uk, when is memorial day 2018

Tab Name: Answer

Source: timeanddate.com

These are the important fields from the IA page. Please check these for errors or missing information and update the IA page

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This is an automated message which will be updated as changes are made to the IA page

[moollaza]

@machineloop apologies for the delay on reviewing. If it's not already there, can you also update the shell script to deduplicate the files?

Thanks!