update api links to point to new docs (#548)

## 📝 Description

**What does this PR do and why is this change necessary?**

Updated all instances of developers.linode.com to techdocs.akamai.com.

README.md

@@ -5,7 +5,7 @@
 [![GoDoc](https://godoc.org/github.com/linode/linodego?status.svg)](https://godoc.org/github.com/linode/linodego)
 [![Go Report Card](https://goreportcard.com/badge/github.com/linode/linodego)](https://goreportcard.com/report/github.com/linode/linodego)
 
-Go client for [Linode REST v4 API](https://developers.linode.com/api/v4)
+Go client for [Linode REST v4 API](https://techdocs.akamai.com/linode-api/reference/api)
 
 ## Installation
 
@@ -17,7 +17,7 @@ go get -u github.com/linode/linodego
 
 See [godoc](https://godoc.org/github.com/linode/linodego) for a complete reference.
 
-The API generally follows the naming patterns prescribed in the [OpenAPIv3 document for Linode APIv4](https://developers.linode.com/api/v4).
+The API generally follows the naming patterns prescribed in the [OpenAPIv3 document for Linode APIv4](https://techdocs.akamai.com/linode-api/reference/api).
 
 Deviations in naming have been made to avoid using "Linode" and "Instance" redundantly or inconsistently.
 

instances.go

@@ -10,7 +10,7 @@ import (
 )
 
 /*
- * https://developers.linode.com/v4/reference/endpoints/linode/instances
+ * https://techdocs.akamai.com/linode-api/reference/post-linode-instance
  */
 
 // InstanceStatus constants start with Instance and include Linode API Instance Status values

profile_tokens.go

@@ -16,7 +16,7 @@ type Token struct {
 	ID int `json:"id"`
 
 	// The scopes this token was created with. These define what parts of the Account the token can be used to access. Many command-line tools, such as the Linode CLI, require tokens with access to *. Tokens with more restrictive scopes are generally more secure.
-	// Valid values are "*" or a comma separated list of scopes https://developers.linode.com/api/v4/#o-auth
+	// Valid values are "*" or a comma separated list of scopes https://techdocs.akamai.com/linode-api/reference/get-started#oauth-reference
 	Scopes string `json:"scopes"`
 
 	// This token's label. This is for display purposes only, but can be used to more easily track what you're using each token for. (1-100 Characters)