ENH: Option to avoid "center" environment.
ENH: Silence test output

A simple patch that makes minimal changes to tests that silences almost all output.
Most fixes were simply changing options to not output (e.g. disp=False), and a few
others trapped errors.

A new class was introduced in tools/testing.py that allows general output in a test
to be silenced.  It would be preferred for code to only raise warnings and not simply
print, so that the warning could be captured instead.
ENH: Converted parallel message to warning

parallel_funciton was printing a warning, but not raising one.  Converted to
a ModuleNotAvailableWarning.

Removed the 'catch all' class that was trapping this test.  Catching all text is
generally a bad idea.
ENH: Separated warnings from other code into a new file

sm_exceptions.py now holds all custom warnings and errors. ConvergenceWarning
was moved to this new module, and imports were corrected.
BUG: Correct derivative for exponential transform.
Merge pull request #1540 from jseabold/fix-1539

BUG: Correct derivative for exponential transform.
Merge pull request #1507 from bashtage/silence-tests

CLN: Silence test output
ENH: Avoid RuntimeWarning when hessian unused
TST: Remove unnecessary test.
Merge pull request #1543 from jseabold/tst-fix-warning

TST: Suppress RuntimeWarning for L-BFGS-B
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
Merge pull request #1438 from toobaz/uncentered_table

ENH: Option to avoid "center" environment.
COMPAT: Add NumpyVersion from scipy
Merge pull request #1432 from jseabold/fix-loose-version

COMPAT: Add NumpyVersion from scipy
MAINT: Deprecate rank in favor of np.linalg.matrix_rank
COMPAT: Add np.linalg.matrix_rank for <= 1.7.1