update README  #2

use minitest gem  #2

add tests for modlue "Gyazz" #2

add tests for class Gyazz::Wiki  #2

raise Gyazz::Error if HTTP request failed

add tests for Gyazz::Wiki#auth  #2

add tests for Gyazz::Page  #2
Merge pull request #3 from shokai/1_test

add Tests