Merge pull request #4207 from iainelder/intro-docs-improvements

Note more secure ways to pass credentials.

website/source/intro/getting-started/build-image.html.md

@@ -113,6 +113,10 @@ With a properly validated template. It is time to build your first image. This
 is done by calling `packer build` with the template file. The output should look
 similar to below. Note that this process typically takes a few minutes.
 
+-> **Note:** For the tutorial it is convenient to use the credentials in the
+command line. However, it is potentially insecure. See our documentation for
+other ways to [specify Amazon credentials](/docs/builders/amazon.html#specifying-amazon-credentials).
+
 -> **Note:** When using packer on Windows, replace the single-quotes in the 
 command below with double-quotes.