Add answers for ex01 and ex02
Add answers to ex03
Add answer for ex04
Add answer to the ex05
Add answers for ex06 and ex07
Add answer to ex08 and ex09
Fix behaviour of takeWhile and dropWhile
Fix type signature
Remove unnecessary binds
Fix typo
Change parity bit to the beginning of binary number

* give better function names
* use sum to compute the parity bit
Merge pull request #7 from fabioyamate/ch07

Chapter 7: Higher-order functions