begin transition from harvest api v1 to v2

* update authentication method required for new v2 of the api
* add additional required config variables for tap usage
* update access_token request to comply with v2 of api
* update schemas to reflect data returned from the v2 api
* add additional schemas to reflect additional data points available

@see https://help.getharvest.com/api-v2/
@see singer-io#9

.gitignore

@@ -95,4 +95,5 @@ ENV/
 # Custom stuff
 env.sh
 config.json
+state.json
 .autoenv.zsh

setup.py

@@ -24,17 +24,28 @@
           'tap_harvest/schemas': [
               "clients.json",
               "contacts.json",
+              "estimate_item_categories.json",
+              "estimate_line_items.json",
+              "estimate_messages.json",
+              "estimates.json",
               "expense_categories.json",
               "expenses.json",
+              "external_reference.json",
               "invoice_item_categories.json",
-              "invoice_payments.json"
+              "invoice_messages.json",
+              "invoice_payments.json",
+              "invoice_recipients.json",
               "invoices.json",
-              "people.json",
               "project_tasks.json",
               "project_users.json",
               "projects.json",
+              "roles.json",
               "tasks.json",
               "time_entries.json",
+              "time_entry_external_reference.json",
+              "user_projects.json",
+              "user_roles.json",
+              "users.json",
           ],
       },
       include_package_data=True,