fix docs, add gemfile

{{cookiecutter.packer_name}}/Gemfile

@@ -0,0 +1,4 @@
+source "http://rubygems.org"
+
+gem "rake"
+gem "popen4"

{{cookiecutter.packer_name}}/README.md

@@ -10,18 +10,7 @@
 
 ## Usage
 
-Finding a suitable base AMI to build from
-
-```
-aws ec2 describe-images --region {{ cookiecutter.aws_region }} \
- --filters Name=image-type,Values=machine \
- --filters Name=owner-id,Values=099720109477 \
- --filters Name=tag-value,Values={{ cookiecutter.target_os_version }} \
- --filters Name=virtualization-type,Values=hvm  \
- --filters Name=architecture,Values=x86_64 \
- --filters Name=root-device-type,Values=ebs \
-  | jq '.Images[] | .Name + "," + .ImageId'  |egrep "{{ cookiecutter.target_os }}/images/hvm-ssd/{{ cookiecutter.target_os }}-{{ cookiecutter.target_os_version }}-" |sort -rn 
-```
+The AMI is automatically  chose see packer.json