converting submodules to be private

**NOT READY FOR MERGE**, just letting the tests run as I go. 
Ok, so deleted the outdated ``ssw_wrapper.so`` wrapper and I do get the error. After making this change I get the following error that @ebolyen and I were looking at this morning:

```
$ kpyc ; nosetests --with-doctest; pep8 skbio/ setup.py
E
======================================================================
ERROR: Failure: ImportError (dynamic module does not define init function (init_ssw_wrapper))
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/caporaso/.virtualenvs/skbio/lib/python2.7/site-packages/nose/loader.py", line 414, in loadTestsFromName
    addr.filename, addr.module)
  File "/Users/caporaso/.virtualenvs/skbio/lib/python2.7/site-packages/nose/importer.py", line 47, in importFromPath
    return self.importFromDir(dir_path, fqname)
  File "/Users/caporaso/.virtualenvs/skbio/lib/python2.7/site-packages/nose/importer.py", line 94, in importFromDir
    mod = load_module(part_fqname, fh, filename, desc)
  File "/Users/caporaso/Dropbox/code/scikit-bio/skbio/__init__.py", line 65, in <module>
    from skbio.alignment import (
  File "/Users/caporaso/Dropbox/code/scikit-bio/skbio/alignment/__init__.py", line 225, in <module>
    from ._ssw import (
  File "/Users/caporaso/Dropbox/code/scikit-bio/skbio/alignment/_ssw/__init__.py", line 9, in <module>
    from ._ssw_wrapper import (
ImportError: dynamic module does not define init function (init_ssw_wrapper)

----------------------------------------------------------------------
Ran 1 test in 0.195s

FAILED (errors=1)
^C... stopped
(skbio)11:28:37 scikit-bio@issue-562$ git diff
diff --git a/skbio/alignment/_ssw/__init__.py b/skbio/alignment/_ssw/__init__.py
index 1515f1d..87c81e5 100644
--- a/skbio/alignment/_ssw/__init__.py
+++ b/skbio/alignment/_ssw/__init__.py
@@ -6,7 +6,7 @@
 # The full license is in the file COPYING.txt, distributed with this software.
 # -----------------------------------------------------------------------------

-from .ssw_wrapper import (
+from ._ssw_wrapper import (
     StripedSmithWaterman, local_pairwise_align_ssw, AlignmentStructure)

 __all__ = ['StripedSmithWaterman', 'AlignmentStructure',
```