[BioRuby] BioRuby tutorial

[Michael O'Keefe]

Hello everyone,

I've updated the tutorial located in the Git repository to add in some 
information that was missing and update the grammar. I created a pull 
request on bioruby/bioruby from my repository at 
https://github.com/okeefm/bioruby
The pull request is at: https://github.com/bioruby/bioruby/pull/32
Please feel free to comment on it; it's my first pull request for 
BioRuby, so I would like to know what I've done well/not well.

Thank you,
Michael O'Keefe
mikeco57 at gmail.com