Proof-reading of chapter 1

Hi Folgert,

I have gone through chapter 1.  I like the content.  I think if we can have them familiar with the object types listed there and have them manipulating those types with conditionals and loops by the end of the first day, that would be great.  I don't think that it is too long, but I guess we will find out.
The only changes I made were grammatical, spelling, etc. changes to clean up the English a bit.  Looking at the diff, it looks like I also changed 'outputs'.  I am not sure how I did that, but if it is something that shouldn't have been changed, ignore it.
Also, let me know how this format of forking and pulling is working.  Like I said, I really have never used GitHub for collaboration before.  I am interested in how well it works.

Matt