Update installation instructions for Fedora

clang 3.7.0 is known to be buggy, and we recommend that people use
3.7.1. Update install instructions to point to 3.7.1.

Compiling BCC on Fedora requires elfutils-libelf-devel. Add this
package to the install instructions for Fedora.

INSTALL.md

@@ -172,7 +172,8 @@ sudo make install
 
 ```
 sudo dnf install -y bison cmake ethtool flex git iperf libstdc++-static \
-  python-netaddr python-pip gcc gcc-c++ make zlib-devel
+  python-netaddr python-pip gcc gcc-c++ make zlib-devel \
+  elfutils-libelf-devel
 sudo dnf install -y luajit luajit-devel  # for Lua support
 sudo dnf install -y \
   http://pkgs.repoforge.org/netperf/netperf-2.6.0-1.el6.rf.x86_64.rpm
@@ -182,8 +183,8 @@ sudo pip install pyroute2
 ### Install binary clang
 
 ```
-wget http://llvm.org/releases/3.7.0/clang+llvm-3.7.0-x86_64-fedora22.tar.xz
-sudo tar xf clang+llvm-3.7.0-x86_64-fedora22.tar.xz -C /usr/local --strip 1
+wget http://llvm.org/releases/3.7.1/clang+llvm-3.7.1-x86_64-fedora22.tar.xz
+sudo tar xf clang+llvm-3.7.1-x86_64-fedora22.tar.xz -C /usr/local --strip 1
 ```
 
 ### Install and compile BCC