Merge pull request #6 from xiehuc/master

finish chapter method
Free should be freedom not no charge.
成为 should be 称为。
a 的 is missing.
Merge pull request #7 from DeathKing/master

Some small fixed.
finish function chapter section 1,2,3

Signed-off-by: xiehuc <xiehuc@gmail.com>
finish function chapter section 4

Signed-off-by: xiehuc <xiehuc@gmail.com>