Simplify gemspec
Use Bundler for gem development dependencies
Add a Rakefile so you can `rake test`

This also includes gem tasks, e.g. `rake release` for simplifying gem
release and version tagging.
Simplify tests
Simplify version
Separate and simplify encoding and decoding
Simplify and convert text files into markdown
Fix indentation in gemspec
Fix typo in license link
Merge pull request #7 from lassebunk/simplify

Simplify and modernize Base62

@lassebunk, thanks for all your efforts. It looks lots better!