Update README.md

README.md

@@ -26,7 +26,7 @@ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
 DEALINGS IN THE SOFTWARE.
 
-## Implement methods
+## Implemented methods
 
 ### IO
  - http://doc.ruby-lang.org/ja/1.9.3/class/IO.html