Do not validate credentials are provided

Also removes the authenticate option as a way to bypass credential
validation.

lib/dnsimple/client.rb

@@ -169,10 +169,8 @@ def request(method, path, data = nil, options = {})
     private
 
     def request_options(custom_options = {})
-      authenticate = custom_options.delete(:authenticate) { true }
-
       options = base_options
-      Extra.deep_merge!(options, auth_options(authenticate))
+      Extra.deep_merge!(options, auth_options)
       Extra.deep_merge!(options, proxy_options)
       Extra.deep_merge!(custom_options, options)
     end
@@ -198,15 +196,13 @@ def proxy_options
       options
     end
 
-    def auth_options(authenticate)
+    def auth_options
       options = {}
 
       if password
         options = { basic_auth: { username: username, password: password } }
       elsif access_token
         options = { headers: { HEADER_AUTHORIZATION => "Bearer #{access_token}" } }
-      else
-        !authenticate or raise Error, "A password, domain API token or access token is required."
       end
 
       options

spec/dnsimple/client_spec.rb

@@ -43,22 +43,6 @@
       expect(WebMock).to have_requested(:get, "https://api.dnsimple.com/test").
           with { |req| req.headers["Authorization"] == "Bearer access-token" }
     end
-
-    it "raises an error if there's no password, domain token or access token provided" do
-      subject = described_class.new(username: "user", oauth_client_id: "id", oauth_client_secret: "secret")
-
-      expect {
-        subject.execute(:get, "test", {})
-      }.to raise_error(Dnsimple::Error, "A password, domain API token or access token is required.")
-    end
-
-    it "can perform requests without requiring authentication" do
-      stub_request(:any, %r{/test})
-
-      expect {
-        subject.execute(:get, "test", nil, authenticate: false)
-      }.not_to raise_error
-    end
   end
 
   describe "#get" do
@@ -192,7 +176,7 @@
           and_return(double('response', code: 200))
 
       subject = described_class.new(proxy: "example-proxy.com:4321")
-      subject.request(:get, "test", nil, authenticate: false)
+      subject.request(:get, "test", nil, {})
     end
   end