Add init_app and init_blueprint methods#1

Need to add `init_app` and `init_blueprint` mehtods to the `LazyViews` class, to have ability use next syntax on initializing plugin: ``` from flask import Flask from flask.ext.lazyviews import LazyViews app = Flask(__name__) views = LazyViews() views.init_app(app) ``` or for blueprints: ``` from flask import Blueprint from flask.ext.lazyviews import LazyViews blueprint = Blueprint('blueprint', __name__) views = LazyViews() views.init_blueprint(blueprint) ```