Update readme for Fedora 23

These are the dependencies required to build in a Fedora 23 Docker
image.

Signed-off-by: Joel Stanley <joel@jms.id.au>
diff --git a/README b/README
index 81b1f6c..a1b969d 100644
--- a/README
+++ b/README
@@ -21,24 +21,9 @@
 
 1. Install Fedora 20 64-bit.
 2. Install the packages necessary for the build:
-> sudo yum update vim-minimal
-> sudo yum install vim gcc-c++ flex bison git ctags cscope expat-devel patch glibc-devel.i686 libgcc.i686 zlib-devel zlib-static libstdc++.i686 libxml2-devel.i686
-3. Install PERL modules necessary for the build:
->  sudo yum install "perl(XML::Simple)" "perl(YAML)" "perl(XML::SAX)" "perl(Fatal)" "perl(Thread::Queue)" "perl(Env)" "perl(XML::LibXML)" "perl(Digest::SHA1)"
-
-Troubleshooting
-===============
-
-* If git is complaining about "fatal: reference is not a tree" with a commit matching a buildroot change, try:
-> rm -rf op-build/buildroot
-> cd op-build
-> git clone --recursive git@github.com:open-power/buildroot.git
-
-
-* If make is complaining during skiboot link phases, revert make to version 3.81
--- On Fedora
---> sudo rpm -del --nodeps make
---> sudo wget ftp://fr2.rpmfind.net/linux/centos/6.5/os/x86_64/Packages/make-3.81-20.el6.x86_64.rpm
---> sudo rpm --install make-3.81-20.el6.x86_64.rpm
-
-(instructions for make reversion from http://curiositydrivendevelopment.blogspot.com)
+> sudo dnf install vim gcc-c++ flex bison git ctags cscope expat-devel patch \
+		zlib-devel zlib-static make unzip tar bzip2 python wget cpio \
+		bc xz findutils perl-XML-Simple perl-Thread-Queue perl-Env   \
+		perl-XML-LibXML perl-Digest-SHA1 perl-bignum libxml2-devel   \
+		libxslt hostname
+3. Continue with the clone, environment setup, and build as noted above.