code updates for better compatibility with other NumPy versions and to fix some bugs

[rmandelb]

Hi @ptorrey and @gsnyder206 ,

In the course of trying to run the sunpy code, my students and I encountered some bugs that I have fixed on a fork, and also found that some lines of code did not work with our versions of NumPy. In the latter case, I extended the code on my fork to work with the new versions of NumPy (without breaking its old functionality either). This pull request is to enable you to integrate these changes with your code base, if you are interested.

I also have noted at one place in sunpy__synthetic_image.py that an error message says to download a file that doesn't seem to exist. I can't fix that since I don't know where the file actually is, but I've flagged it so you can update it.

In case you aren't used to the GitHub interface for viewing code changes, I suggest you click on the tab that says "4 files changed". It lets you see all the changes line-by-line, and you can also see where I've made a comment suggesting an update in sunpy__synthetic_image.py.

I hope this is helpful, but please let me know if you have any questions!