Update lisp practice code
Merge pull request #8 from wkentaro/wkentaro

Add lisp examples
Add page location
Merge pull request #9 from ken0nek/ken0nek

Add page location
Update 9.l
Add solution of the problem below
'nilでない要素の合計を書こうとしたが...'
Merge pull request #10 from wkentaro/wkentaro

Update practice problem on the textbook distributed on 2014-10-22