Concurrency fix for example in "Count number of hosts by application group"

When the previous code was called concurrently old values might be applied instead of changing the value atomically.
Merge pull request #260 from digital-science/gh-pages

Thank Federico Borgnia
Merge pull request #256 from jeroenvandijk/patch-2

Concurrency fix for example in "Count number of hosts by application gro...
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Merge branch 'gh-pages' of github.com:aphyr/riemann into gh-pages

Conflicts:
	thanks.html
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Whitespace
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Merge branch 'gh-pages' of github.com:aphyr/riemann into gh-pages
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Thank Mark Feeney
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Merge branch 'gh-pages' of github.com:aphyr/riemann into gh-pages
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Thank Michael Fairley
Thank pyr
fix "adjust" example as per API reference

Copy-pasting the previous form results in this error:
java.lang.ClassCastException: java.lang.String cannot be cast to clojure.lang.IFn
Merge pull request #270 from mfournier/adjust-mistake

fix "adjust" example as per API reference