Added images for second intro to Radio Astronomy section

Images for 2_Interferometry.ipynb and 2_Interferometry_Solution
in 1_Introduction_to_Radio_Astronomy
Edit to griddata options for be matplotlib 1.4.0 compatible

Added the interp option to griddata in notebook:
1_Single-Dish_Data_Analysis.ipynb
In order to be matplotlib 1.4.0 compatible.