[Halld-offline] heads-up: pull requests require review for halld_recon and halld_sim

[Mark Ito]

Folks,

At the software meeting just now, we decided to require "reviews" of 
pull requests before they can be merged onto the master branch. For now 
this is only for halld_sim and halld_recon. The webpages for the 
individual pull requests now reflect this. The idea is to prevent 
inadvertent changes to the master branches.

   -- Mark