add pig to edge node
fix resourcemanager issues

restart resourcemanager only when it's running and yarn-site.xml changes
handle better when yarn or classic MR are not installed
hosts file template
add example of an instance type using spot instances
added note about boto in advance of commenting out the boto play
removing boto installation

Since people sometimes use virtualenv rather than installing modules in the system locations, let's let them get boto in whatever way they decide is best.