NF: get_unscaled method for Analyze array proxy

Add get_unscaled for those of us who like to get the raw unscaled data
from the array.
TST: tests for read_img_data function

Test the behavior of the `read_img_data` function as of commit 6d8f6c6.
This is before the changes to Analyze image types to make the header
slope, intercept and data offset be consumed during write, and reset to
default values.  These tests pass against that commit but fail against
current master, which is 62f4c70.
RF: replicate read_img_data behavior + deprecate

Do approximate replication of the old behavior of read_img_data.

Deprecate with suggestions about alternatives.
RF: allow generic header to specify memory layout

Just in case someone needs the generic header to write in C order rather
than F order.
BF: fix invalid call to parent in minc classes

It was possible to call `data_from_fileobj` and `data_to_fileobj` from a
generic Header object, and the MINC classes use that object, so these
could cause confusion by making invalid calls.  Raise
NotImplementedError to reduce potential confusion.
RF: bdist_wheel, bdist_mpkg as setuptools commands

Make sure setup uses setuptools for specialized setup commands needing
setuptools.
Merge pull request #226 from matthew-brett/remove-minc-header-data-fetch

MRG: fix invalid call to parent in minc classes

Prevent invalid call to the minc header-like class.
Merge pull request #225 from matthew-brett/generalize-header-data-layout

RF: allow generic header to specify memory layout

Header base class can specify C as well as Fortran memory layout.
RF: removed unused argument in class init

chdir argument unused in TemporaryDirectory init
fix endian value in gifti
fix b64encoding for no newline in outputs
fixes + backcompat test
NF: add setuptools-aware package checking

Add extra dictionary arg to package_check so that package_check knows
its working with setuptools, and can fill the dependencies in the
dictionary accordingly.
RF: adapt setup.py dependency checks to setuptools.

This is still a disaster if running normal ``python setup_egg.py
install`` - but no more of a disaster than before.
TST+BF: extend comments and tests on bad gii file

Luckily one of our test files uses a couple of bad encoding values, and
carriage returns in base64 data.  Comment on this and add explicit
checks of endianness.
TST: check gifti bad contents gets written as good

Check for presence of bad tags and their removal by loading and saving
the file.
BF+RF: refactor base64 and array to text for py3

Refactor base64 imports to use the standard interface.

Replace use of np.savetxt and BytesIO with a small custom function for
writing comma-delimited text.  Fixes Python 3 incompatibility mixing
output from BytesIO with strings.
RF: remove duplicate test

We're testing backwards compatibility in `test_base64_written`
TST: add round trip tests for example images

Add tests for saved / loaded example images.
Merge pull request #234 from nipy/package_check-fix

MRG: adapt package_check to setuptools

Now pip is working pretty well, adapt package_check to fill setuptools
arguments instead of giving errors, when setuptools has been imported.