add 3 ok exercises from sunrise
add 1 revised exercise from ej
Merge branch 'ej_1203'
修改【20141203】——Understand_coins
Merge branch 'sunrise_1205_Understand_coins'
修改【20141203】——combinations_of_polynomials
Merge branch 'sunrise_1205_combinations_of_polynomials'
修改【20141203】——date_and_weekday
Merge branch 'sunrise_1205_date_and_weekday'
修改【20141203】——millimeter_and_centimeter
Merge branch 'sunrise_1205_millimeter_and_centimeter'
修改【20141203】——application_of_linear_equations_1
Merge branch 'sunrise_1205_application_of_linear_equations_1'
修改【20141205】——dividing_decimals
Merge branch 'sunrise_1205_dividing_decimals'
修改【20141205】——multiplying_and_dividing
Merge branch 'sunrise_1205_multiplying_and_dividing'
修改【20141208】——morning_afternoon_night,number_line_0.5,number_line_0.7,number_line_4
Merge branch 'sunrise_1208all'
new "separation_and_union" exercise made by sunrise1208