Fix capitals: `string` -> `String`, & 'To' -> 'to'

This fixes 2 very tiny typos.

When talking about monkeys eventually typing out 
"to be or not to be," and how it's a silly example,
the example sketch has 2 problems:

1. the java class String was lower-cased
2. the sentence, which was supposed to only have lower-case, started with a capital T

This fixes both of those.
Merge pull request #310 from danbernier/master

Fix for 2 (tiny) typos in chapter 9