Optional showing of percentage text

In reference to https://github.com/CollectionFS/Meteor-cfs-ui/issues/9, I have forked and implemented the feature. I also went ahead and addressed the documentation issue (https://github.com/CollectionFS/Meteor-cfs-ui/issues/8) and updated the documentation to show the added feature. Lastly, I updated the package.js to 0.0.2 and bumped the version numbers of the api.use commands. I'm not sure if you wanted this last part to happen, but I did it anyway.

- Added support for the optional text overlay of the progress bar using "showPercent" attribute on the context.
- Updated README.md to show this new flag
- Updated README.md to accurately reflect that, with the most recent version of bootstrap, it is possible to have animated, striped progress bars without modifying an outer div