update recipe to use attribute

Currently, the code will enforce only revision 0.6.5, instead of
allowing the user-defined attribute to take precedence over the default
version.
remove duplicate git package

When executing, this triggers a resource clong, per CHEF-3694.
add install_method, version attributes and behavior

Switch behaviors between source install from git vs pip package install.
Enable setting :version for both package and source.
Merge pull request #9 from DataDog/miketheman/integration

3 Changes, all in one clean PR