Remove prereq check from install.rb
Remove prereq check from install.rb

The json backend is an optional component of hiera. Json is a dependency of our
packages but doesn't need to be there before install.rb can be run. This commit
removes the prereq list and checks from install.rb.

Iristyle/hiera,Iristyle/hiera,johnduarte/hiera,justinstoller/hiera,MikaelSmith/hiera,johnduarte/hiera,MikaelSmith/hiera,MikaelSmith/hiera,ferventcoder/hiera,johnduarte/hiera,justinstoller/hiera,hlindberg/hiera,Iristyle/hiera,hlindberg/hiera,hlindberg/hiera,ferventcoder/hiera,justinstoller/hiera,ferventcoder/hiera