setup.py crashes if numpy is not installed before cartopy

[rune-bk]

This crashes the setup if numpy is not installed by pip before cartopy.

cartopy/setup.py

Lines 59 to 62 in 60ae9a6

	try:
	import numpy as np
	except ImportError:
	raise ImportError('NumPy 1.10+ is required to install cartopy.')

Given that it is already in the requirements this block of code should be removed?

[greglucas]

It is in the requirements, but it is also needed for installation I believe, so needs an install_requires as well. See also issue #1552, which I think is similar to this.

[dopplershift]

install_requires is for run/import-time dependencies. setup_requires is for install-time dependencies (need to run setup.py).

[QuLogic]

I believe this is fixed by #1681.