if a newer rubocop version is installed, pdk should fall-back to safe defaults

[igalic]

When installing pdk from source (or gem) it doesn't pull in a rubocop dependency… However, when there already is a rubocop installed in a newer version than it wants, rather than falling back on its safe defaults, it throws the following error:

pdk (DEBUG): Rendering '.rubocop.yml.erb'...
pdk (FATAL): Failed to render template '.rubocop.yml.erb'
RuntimeError: no defaults for rubocop 0.52.1 available
pdk (DEBUG): RuntimeError: no defaults for rubocop 0.52.1 available
pdk (DEBUG): /tmp/pdk-templates20180207-4255-1trn9z4/moduleroot/.rubocop.yml.erb:39:in `render_erb'
pdk (DEBUG): /home/igalic/.rbenv/versions/2.4.3/lib/ruby/2.4.0/erb.rb:896:in `eval'
pdk (DEBUG): /home/igalic/.rbenv/versions/2.4.3/lib/ruby/2.4.0/erb.rb:896:in `result'
pdk (DEBUG): /home/igalic/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/pdk-1.3.2/lib/pdk/template_file.rb:75:in `render_erb'
pdk (DEBUG): /home/igalic/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/pdk-1.3.2/lib/pdk/template_file.rb:41:in `render'
pdk (DEBUG): /home/igalic/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/pdk-1.3.2/lib/pdk/module/templatedir.rb:129:in `block in render'
pdk (DEBUG): /home/igalic/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/pdk-1.3.2/lib/pdk/module/templatedir.rb:124:in `each'
pdk (DEBUG): /home/igalic/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/pdk-1.3.2/lib/pdk/module/templatedir.rb:124:in `render'
pdk (DEBUG): /home/igalic/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/pdk-1.3.2/lib/pdk/module/convert.rb:24:in `block in invoke'
pdk (DEBUG): /home/igalic/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/pdk-1.3.2/lib/pdk/module/templatedir.rb:82:in `initialize'
pdk (DEBUG): /home/igalic/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/pdk-1.3.2/lib/pdk/module/convert.rb:13:in `new'
pdk (DEBUG): /home/igalic/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/pdk-1.3.2/lib/pdk/module/convert.rb:13:in `invoke'
pdk (DEBUG): /home/igalic/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/pdk-1.3.2/lib/pdk/cli/convert.rb:27:in `block (2 levels) in <module:CLI>'
pdk (DEBUG): /home/igalic/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/cri-2.9.1/lib/cri/command.rb:319:in `run_this'
pdk (DEBUG): /home/igalic/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/cri-2.9.1/lib/cri/command.rb:264:in `run'
pdk (DEBUG): /home/igalic/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/cri-2.9.1/lib/cri/command.rb:282:in `run'
pdk (DEBUG): /home/igalic/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/pdk-1.3.2/lib/pdk/cli.rb:17:in `run'
pdk (DEBUG): /home/igalic/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/pdk-1.3.2/exe/pdk:6:in `<top (required)>'
pdk (DEBUG): /home/igalic/.rbenv/versions/2.4.3/bin/pdk:23:in `load'
pdk (DEBUG): /home/igalic/.rbenv/versions/2.4.3/bin/pdk:23:in `<main>'