Add env var for article batch size, set default to 3

[dylano]

Fixes #124

Set default batch size to 3 articles and add a ARTICLE_BATCH_SIZE to override if necessary.

[dylano]

Note that I am programatically skipping the tests for "Fourth" and "Fifth" if the article batch size is less than 4 or 5, so with the default value of 3, you will see some pending tests.

[coveralls]

Pull Request Test Coverage Report for Build 60

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 8 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-1.8%) to 77.514%

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Files with Coverage Reduction	New Missed Lines	%
state_handlers.js	8	81.55%
<!--	Total:	8		-->

Totals
Change from base Build 56:	-1.8%
Covered Lines:	371
Relevant Lines:	465

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💛 - Coveralls