Warn about upcoming API change

Author: stilvoid

README.md

@@ -26,59 +26,6 @@ Options:
 
 ### Go package documentation
 
-```go
-import "github.com/awslabs/aws-cloudformation-template-formatter/format"
-```
-
-Package format provides functions for formatting CloudFormation
-templates using an opinionated, idiomatic format as used in AWS
-documentation.
-
-For each function, CloudFormation templates should be represented using
-a `map[string]interface{}` as output by other libraries that parse
-JSON/YAML such as `github.com/awslabs/goformation` and `encoding/json`.
-
-Comments can be passed along with the template data in the following
-format:
-
-```go
-map[interface{}]interface{}{
-    "": "This is a top-level comment",
-    "Resources": map[interface{}]interface{}{
-        "": "This is a comment on the whole `Resources` property",
-        "MyBucket": map[interface{}]interface{}{
-            "Properties": map[interface{}]interface{}{
-                "BucketName": "This is a comment on BucketName",
-            },
-        },
-    },
-}
-```
-
-Empty string keys are taken to represent a comment on the overall node
-that the comment is attached to. Numeric keys can be used to reference
-elements of arrays in the source data.
-
-#### Functions
+**The API for cfn-format will be changing in 1.0.0**
 
-```go
-func Json(data map[string]interface{}) string
-    Json formats the CloudFormation template as a Json string
-```
-
-```go
-func JsonWithComments(data map[string]interface{}, comments map[interface{}]interface{}) string
-    JsonWithComments formats the CloudFormation template as a Json string
-    with comments as provided
-```
-
-```go
-func Yaml(data map[string]interface{}) string
-    Yaml formats the CloudFormation template as a Yaml string
-```
-
-```go
-func YamlWithComments(data map[string]interface{}, comments map[interface{}]interface{}) string
-    YamlWithComments formats the CloudFormation template as a Yaml string
-    with comments as provided
-```
+To see the current Go documentation for cfn-format, please check <format/doc.go>.