Tidying the text up

[zelima]

@rgrp could you please give suggestions.

[rufuspollock]

e.g. suggest

Time series data of major commodity prices and indexes like iron, cooper, wheat, gold, oil, food price index etc... Data comes frome International Monetary Fund (IMF)

Should be:

Time series of major commodity prices and indices including iron, cooper, wheat, gold, oil. Data comes from the International Monetary Fund (IMF).

Other items

Source heading is not needed in "Data" - just have a link or sentence.

There should be a License section with some information e.g. what are the terms on the original dataset etc.

[zelima]

@rgrp please review new README