Modify Gemspec and fix problems with vSphere CentOS template

Reverted Gemspec entry for em-winrm to use git:// instead of http://

Added a vsphere group to the Gemspec to hold vsphere specific
dependencies, per reviewer recommendations.

Removed vsphere specific gems (i.e., rbvmomi) from veewee.gemspec

Fixed two errors in CentOS vSphere template: ks.cfg referenced a local
OS location from original testing, and a postinstall2.sh file was
committed in error.

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
# On branch vsphere-support
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#	modified:   Gemfile
#	modified:   lib/veewee/provider/vsphere/box/create.rb
#	modified:   templates/CentOS-5.8-x86_64-netboot-vsphere/ks.cfg
#	deleted:    templates/CentOS-5.8-x86_64-netboot-vsphere/postinstall2.sh
#	modified:   veewee.gemspec
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#	experiment/