Add beta warning and todos (anchore#136)

* Add future ideas + beta warning to README

Signed-off-by: Ross Turk <ross@rossturk.com>

* Update link

Signed-off-by: Ross Turk <ross@rossturk.com>

README.md

@@ -14,6 +14,8 @@ A CLI tool and go library for generating a Software Bill of Materials (SBOM) fro
 - Supports packages and libraries from various ecosystems (APK, DEB, RPM, Ruby Bundles, Python Wheel/Egg/requirements.txt, JavaScript NPM/Yarn, Java JAR/EAR/WAR, Jenkins plugins JPI/HPI, Go modules)
 - OS distribution detection (supports alpine, busybox, centos/redhat, debian/ubuntu flavored distributions)
 
+> :warning: **This is pre-release software** and it may not work as expected. If you encounter an issue, please [let us know using the issue tracker](https://github.com/anchore/syft/issues).
+
 ## Getting started
 
 To generate an SBOM for an image:
@@ -99,3 +101,9 @@ log:
 # enable/disable checking for application updates on startup
 check-for-app-update: true
 ```
+
+## Future plans
+
+The following areas of potential development are currently being investigated:
+- Add CycloneDX to list of output formats
+- Establish a stable interchange format w/Grype