ENH: Alternative travis script that uses Anaconda via Miniconda

Provides an alternative method to test on Travis using Miniconda
that has some advantages from the current system.

- All binary, so no time spent building
- No branching in the execution steps
- Support for up-to-date requirements which are important to test

Also includes a small change to tools/matplotlibrc which changes the backend
to Agg to avoid Tk-related errors on Travis.  Agg is alays available and does not
depend on Qt or another toolkit.

Closes #1500
Changed build configurations to match those discusses in #1523
Fixed config for Python 3.3
Attempt to inspect segfault
Final fixes to remove redundant code from travis config file
Final fixes to remove redundant code from travis config file
Added 4th build configuration

New configuration will always be on the most current versions using Python 2.7
Fixed conda-related issue which allows for no MKL
Added option for cvxopt to Python 2.7, Numpy 1.7 config
Merge pull request #1523 from bashtage/travis-miniconda

MAINT: Use miniconda on Travis.
Merge pull request #1535 from bashtage/2-6-fixes

TST: Fixes for 2.6 test failures, replacing astype(str) with apply(str)
Test coveralls issue removing if, then
Fixed coveragerc to allow anythin in */statsmodels/*
Changes for single coverage run
Merge remote-tracking branch 'remotes/upstream/master' into travis-miniconda
Change test condition for coverage
Fix for missing font warning
Simplification using globals
Marked known fails
Suppressed noise from matplotlib about .matplotlibrc location
Final modifications to simplify coverage choices
Merge pull request #1536 from bashtage/travis-miniconda

BUG: Restores coveralls for a single build
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.