Code cleanup - #51

@bsipocz - thanks! I merged #47, so can you rebase this?

@astrofrog - Rebased.

@leejjoon - I'll leave this open a couple of days in case you want to review this (but I think nothing here is controversial)

@astrofrog - Sure. There're still a handful of commented out code lines. However they may be removed later (e.g. until the code has better test coverage), as I'm not sure why they were left there, whether it was for future reuse, or they can be removed for good.

Nice. I've got a couple suggestions for more unused code that can be removed (this is from a WIP branch):

• In pyregion/region_numbers.py: getSign, and get_degree functions can be removed
• In pyregion/wcs_helper.py:
  • If you import astropy.extern.six, you can remove the is_string_like function and just use isinstance(..., six.string_types)
  • I think the unit fixing in fix_header is already done in astropy
  • At least here, both WCS.ctypes are strings in python2 and python3. So I think the as_str function (and the call(s) to it) can be removed.
  • Big one: nothing uses ProjectionPywcs, ProjectionSimple, ProjectionDefault, estimate_cdelt_trans, or estimate_angle_trans, or is_equal_coord_sys. I guess this would be a public API change, but there are no docs for these things anyways

This might change @astrofrog's comment about nothing being controversal though :/ I've been trying to figure out the code for issue #43, and finding this stuff in the way.

@bsipocz @sargas - thanks to both of you for working on this!

@leejjoon - can you comment on @sargas's suggestions of code that can be removed? Are any of the functions/classes he is suggesting still needed?

I think @sargas suggestions are all harmless. So i have no objection in removing/replacing those things.

@leejjoon Thanks

@bsipocz https://gist.github.com/sargas/654a6dc7f7b3d57a6464 is my changes, but I can do another PR if you'd like to keep these seperate. I was much harsher to commented out code (since it's in git's history if needed, and much is likely to be removed converting from kapteyn to astropy.coordinates)

@sargas - you can actually open a PR to @bsipocz's branch with your changes if you like (but a completely separate PR is also fine).

@sargas - I was just about to write the same as @astrofrog. A third option is to just push your brunch to github, and then I can cherry pick your commit on top of this PR.

@astrofrog @bsipocz Interesting, I didn't realize you could do PR's on PR's. I added bsipocz#1 if you'd like to merge or cherry-pick.

Realizing that they were left out yesterday, I repeated the same cleaning exercise with the cython and test files.

@bsipocz @sargas - thanks for the cleanup! Just a few small comments above, then we should merge this!

@astrofrog - thanks for the comments, they are dealt with in the latest commit.

@bsipocz @sargas - thanks to both of you for your work on this!