[Biopython] Making the tutorial more concise

[Peng Yu]

I feel that the document can be made more concise.

http://biopython.org/DIST/docs/tutorial/Tutorial.html#htoc73

For example, on the above link, it says
"Hey, everybody loves BLAST right? I mean, geez, how can get it get
any easier to do comparisons between one of your sequences and every
other sequence in the known world?"

I think this can be delete. Or it can be simply stated what Chapter 7
is about at the beginning.