README.md improvements, corrections

[tralfamadude]

The getting started info needs to mention how to build and install in case there is no prebuilt tarball:
mvn clean package
cd assembly/target
#note which jclouds-cli-* you will expand for installation in another directory
After expanding the tar or zip or jar, cd to the directory created and run one of the scripts with bin as the relative path, example:
bin/jclouds-cli

These commands are documented, but do not work ("not found") in bin/shell:
features:list
features:install jclouds-api-cloudstack
Later I found that these are in bin/jclouds-cli and that should be clarified.

[iocanel]

Thanks for feedback. I'll update the readme file, hopefully early next week!
Till then if you fancy, sending in a pull request, its always welcome :-)