Hardcoded tmp_root prevents multiple users using the same box for development

[alexjfisher]

I recently discovered

terraspace-bundler/lib/terraspace_bundler/mod/concerns/path_concern.rb

Line 9 in d320470

"/tmp/terraspace/bundler"

causes issues when multiple users try to use terraspace from the same box.

I worked around this by monkey-patching the method at the top of my Terrafile.

module TerraspaceBundler::Mod::Concerns
  module PathConcern
    def tmp_root
      "/tmp/terraspace_#{ENV['USER']}/bundler"
    end
  end
end

@tongueroo Would this be an acceptable solution to submit has a PR, or perhaps a new ENV variable entirely would be more appropriate?
eg.

def tmp_root
  ENV['TS_BUNDLER_TMP_DIR'] || '/tmp/terraspace/bundler'
end

or maybe even...

def tmp_root
  ENV['TS_BUNDLER_TMP_DIR'] || "/tmp/terraspace_#{ENV['USER']}/bundler"
end