Update readme and docstrings, minor refactors.

README.md

@@ -2,7 +2,7 @@
 
 ## Overview [![GoDoc](https://godoc.org/github.com/rhnvrm/simples3?status.svg)](https://godoc.org/github.com/rhnvrm/simples3) [![Go Report Card](https://goreportcard.com/badge/github.com/rhnvrm/simples3)](https://goreportcard.com/report/github.com/rhnvrm/simples3)
 
-SimpleS3 is a golang library for uploading and deleting objects on S3 buckets using the REST API calls signed using AWS Signature Version 4
+SimpleS3 is a golang library for uploading and deleting objects on S3 buckets using REST API calls or Presigned URLs signed using AWS Signature Version 4.
 
 ## Install
 
@@ -16,7 +16,16 @@ go get github.com/rhnvrm/simples3
 testTxt, _ := os.Open("test.txt")
 defer testTxt.Close()
 
+// Create an instance of the package
+// You can either create by manually supplying credentials
+// (preferably using Environment vars)
 s3 := simples3.New(Region, AWSAccessKey, AWSSecretKey)
+// or you can use this on an EC2 instance to 
+// obtain credentials from IAM attached to the instance.
+s3 := simples3.NewUsingIAM(Region)
+
+// File Upload is as simple as providing the following
+// details.
 err := s3.FileUpload(simples3.UploadInput{
     Bucket:      AWSBucket,
     ObjectKey:   "test.txt",
@@ -24,19 +33,34 @@ err := s3.FileUpload(simples3.UploadInput{
     FileName:    "test.txt",
     Body:        testTxt,
 }
+
+// Similarly, Files can be deleted.
+err := s3.FileDelete(simples3.DeleteInput{
+    Bucket:    os.Getenv("AWS_S3_BUCKET"),
+    ObjectKey: "test.txt",
+}
+
+// You can also use this library to generate
+// Presigned URLs that can for eg. be used to
+// GET/PUT files on S3 through the browser.
+var time, _ = time.Parse(time.RFC1123, "Fri, 24 May 2013 00:00:00 GMT")
+
+url := s.GeneratePresignedURL(PresignedInput{
+    Bucket:        "examplebucket",
+    ObjectKey:     "test.txt",
+    Method:        "GET",
+    Timestamp:     time,
+    ExpirySeconds: 86400,
+})
 ```
 
 ## Contributing
 
-ToDo.
-
-## Contributors
-
-ToDo.
+You are more than welcome to contribute to this project. Fork and make a Pull Request, or create an Issue if you see any problem or want to propose a feature.
 
 ## Author
 
-ToDo.
+Rohan Verma <hello@rohanverma.net>
 
 ## License