Correct use of 'nul' 'null' and capitalization in the book#34294

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bors merged 2 commits intorust-lang:masterfrom

alexandermerritt:book-nuls

Jul 6, 2016

Commits on Jun 16, 2016

Correct use of 'nul' 'null' and capitalization
alexandermerritt
committed

Commits on Jun 29, 2016

NULL not back-ticked
alexandermerritt
committed