CLN: Improve warnings to avoid generic warnings messages

All generic Warnings have been replaced with specific warnings, which have
been consolidated into sm_exceptions.py.

Conflicts:
	statsmodels/tools/sm_exceptions.py
Added specific warnings in a couple of places where they were missing

Converted raise Warning to warning.warn

Made certain warnings had been imported in some modules where it was lazily
imported

Simplified warnings in GEE which was neither lazily imported nor imported
at the top of the file
Fix for conda 3.4 changes
Merge pull request #1510 from bashtage/warning-convert

CLN: Improve warnings to avoid generic warnings messages
Merge pull request #1544 from bashtage/travis-miniconda

MAINT: Fix travis miniconda build
CLN: Refactored so that there is no longer a need for 2to3

The codebase has been refactored so that it can exist in a single, unified base.
The strategy closely followed six and pandas.compat, but does not involve any further
dependencies.

The compatability location has been renamed form compatnp, which housed compatnp.py3k, to
just compat, and the main py3k compatability files are in __init__.py so that they can
be directly accessed

Conflicts:
	statsmodels/genmod/tests/test_gee.py
	statsmodels/nonparametric/tests/test_kernels.py
	statsmodels/sandbox/regression/tests/test_gmm.py
	statsmodels/tools/parallel.py
	statsmodels/tsa/vector_ar/tests/test_var.py

Conflicts:
	statsmodels/base/data.py
	statsmodels/tools/decorators.py
Rolled back absolute imports in api.py
Refactored compatnp to compat and moved all py3k to __init__. compatnp
is not the correct name, and it makes more sense for compat to be the
location of any backward/forward compatability code using compat for
the majority of the py3k code and submodules np (or numpy) for numpy and scipy.

Conflicts:
	statsmodels/base/data.py
	statsmodels/tools/decorators.py
Final removal of 2.x print
Fixes reduce-related issues

Conflicts:
	statsmodels/base/data.py
Removes extra .items() and replaced with iteritems.
Corrected typo in import BytesIO
Many small fixes related to things missed that are not covered by tests, including
raw_input
Removed redundant parentheses that produced tuples in print statements
Rolled back a small error in the previous commit
Fix broken execfile fix
Removed unnecessary use of lzip and lmap
Imported zip and map from compat where used
Rebase error fixes
Cleaned up old, out dated import code for packages that are now required.
Removed a small amount of unnecessary compatability code for slogdet

Conflicts:
	statsmodels/iolib/tests/test_table_econpy.py
Further refinements to the compat module
Remove unnecessary compat file