Update INSTALL
Update INSTALL

Replace bare-bones INSTALL with a pointer to DeadDropDocs
chadmiller/securedrop,mark-in/securedrop-prov-upstream,kelcecil/securedrop,heartsucker/securedrop,GabeIsman/securedrop,GabeIsman/securedrop,kelcecil/securedrop,pwplus/securedrop,chadmiller/securedrop,heartsucker/securedrop,harlo/securedrop,conorsch/securedrop,GabeIsman/securedrop,jaseg/securedrop,jaseg/securedrop,micahflee/securedrop,conorsch/securedrop,conorsch/securedrop,mark-in/securedrop-prov-upstream,garrettr/securedrop,harlo/securedrop,jeann2013/securedrop,ehartsuyker/securedrop,jeann2013/securedrop,jrosco/securedrop,ehartsuyker/securedrop,GabeIsman/securedrop,harlo/securedrop,jeann2013/securedrop,garrettr/securedrop,harlo/securedrop,jaseg/securedrop,harlo/securedrop,chadmiller/securedrop,pwplus/securedrop,jaseg/securedrop,ageis/securedrop,jaseg/securedrop,jrosco/securedrop,heartsucker/securedrop,chadmiller/securedrop,pwplus/securedrop,heartsucker/securedrop,jrosco/securedrop,jeann2013/securedrop,jeann2013/securedrop,micahflee/securedrop,conorsch/securedrop,harlo/securedrop,pwplus/securedrop,jrosco/securedrop,ageis/securedrop,conorsch/securedrop,micahflee/securedrop,ehartsuyker/securedrop,kelcecil/securedrop,jaseg/securedrop,kelcecil/securedrop,ehartsuyker/securedrop,mark-in/securedrop-prov-upstream,GabeIsman/securedrop,ageis/securedrop,garrettr/securedrop,micahflee/securedrop,ehartsuyker/securedrop,ehartsuyker/securedrop,mark-in/securedrop-prov-upstream,kelcecil/securedrop,ageis/securedrop,pwplus/securedrop,pwplus/securedrop,chadmiller/securedrop,jeann2013/securedrop,garrettr/securedrop,heartsucker/securedrop,chadmiller/securedrop,kelcecil/securedrop,jrosco/securedrop,jrosco/securedrop,GabeIsman/securedrop