Fixing outdated command in README

As of cfea16ba, the box type is 'virtualbox-iso' and 'vmware-iso' instead of the old 'virtualbox'/'vmware'. Updating the README to
reflect that.
Merge pull request #155 from apetresc/patch-1

Fixing outdated command in README
Don't disable selinux on Fedora; just make it Permissive.
Merge pull request #156 from juliandunn/fedora-selinux-permissive

Don't disable selinux on Fedora; just make it Permissive.
[BENTO-111] Added a .gitattributes and a note in README about Windows hosts
 * A .gitattributes was added to the repository to ensure ks.cfg, preseed.cfg
   and *.sh files have correct LF line endings and *.bat files have
   correct CRLF line endings.
 * Added a note about this in the README so people packaging boxes
   from Windows Hosts can fix the problem if they encounter it.
Tidy up some text in #111
support mirror variable for iso_url in all centos/vmware builders
Merge pull request #158 from adler/master

support mirror variable for iso_url in all centos/vmware builders
Updated to RELEASE from RC4.
Install all virtio kernel modules
Debian 7.3.0 support
 * updated iso url and checksum
 * Use new {virtualbox,vmware}-iso builder names (packer 0.5.0 change)
Allow `packer_cache` to be symlink

The trailing slash ignores only directories.
Merge pull request #161 from tmatilai/packer_cache_symlink

Allow `packer_cache` to be symlink
Merge pull request #159 from juliandunn/freebsd-10

Finalize FreeBSD 10 support
Merge pull request #160 from fadenb/feat/debian-7.3.0

Debian 7.3.0 support