allow challenge tasks to be displayed on challenge page - fixes https://github.com/HabitRPG/habitrpg/issues/4150
replace original challenge fix with negue's suggestion
Merge pull request #4151 from Alys/challengeFix-2014-10-16

allow challenge tasks to be displayed on challenge page - fixes https://github.com/HabitRPG/habitrpg/issues/4150
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Merge pull request #4159 from crookedneighbor/update-landing-page-img

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