Merge pull request #2 from halprin/update-readme

Update README.md

Author: halprin

README.md

@@ -1,2 +1,23 @@
 # delete-dynamodb-items
 Bulk delete items from a DynamoDB table.
+
+## Usage
+
+_**Warning**: running this command will result in all the items in the specified table to be deleted immediately!  There
+is no "are you sure?" prompt._
+
+```shell
+delete-dynamodb-items <table name>
+```
+
+The program uses the default AWS credential algorithm to determine what IAM entity and region is used.  E.g. the
+`~/.aws/credentials` file, the `AWS_*` environment variables, etc.
+
+## Build
+
+Run the following to compile your own copy from source.
+
+```shell
+go get -v -t -d ./cmd/
+go build -o delete-dynamodb-items -v ./cmd/
+```