Deprecated legacy key migration

[svanegasm]

These changes seek to maintain the usability of the gem according to the Legacy Api Key deprecation plan.

Ref:
Legacy Key Deprecation
Schedule for Legacy Key Deprecation
Legacy Key Migration
Personal Access Tokens & Service Account Keys

[jearbot]

Can confirm that this PR solves my issue! Forked this gem and applied these changes and all is golden.

[nateleavitt]

Hey guys.. I know this is late, but I think you can do the same thing with XML-RPC by doing the following:

Infusionsoft.configure do |config|
  config.user_agent = "CustomerHub-#{HUB_VERSION}"
  config.api_key = SAK_KEY
  config.api_url = "api.infusionsoft.com"
  config.use_oauth = true
end

The key change is adding config.use_oauth = true. I'm pretty sure this will work.

[nateleavitt]

Updated Readme