DOC: Add one line docs summary
Merge pull request #2081 from jseabold/docs-fix

DOC: Add one line docs summary
MAINT: Remove redundant rsync flags
Merge pull request #2082 from jseabold/cleanup-rsync

MAINT: Remove redundant rsync flags
TST: Test missing failure with formula.
BUG: combined can be empty if patsy handles missing. Closes #2083.
TST: Test that missing, formula, and extra arrays work.
ENH: Ensure extra arrays are attached as ndarrays.
BUG: Check input array lengths after missing data handling.
TST: Test that missing, formula, and extra arrays work.
BUG: Check input array lengths after missing handling.
TST: Test for extra arrays with missing and formula
BUG: Handle 2d extra arrays and endog/exog with formula and missing.
TST: Update for dimension handling higher up.
ENH: Ensure ndarray-like is passed up. Needs refactor.
Merge pull request #2084 from jseabold/fix-2083

BUG: Correct issue if patsy handles missing. Closes #2083.
ENH: Unit Root Tests

Introduces 4 new unit root tests and adds a class-based
Augmented Dickey Fuller.

The four new tests are:
  - PhillipsPerron
  - KPSS
  - Variance Ratio
  - DF-GLS

These have all been included in unitroot.py, and the afduller function has
been moved from tsatools to unitroot, and is now just a wrapper around the
ADF class.

The critical value and p-value lookup codes have also been consolidated
into untiroot.py.  Critical value and p-value lookup information for DFGLS
and KPSS is not readily available in published form, and so simulations
were performed to generate these using 100,000,000 replications using a
methodology similar to MacKinnon (2010).  All critical value data has
been consolidated into tsa/critical_values.

A cov_nw function was added to tsa/stattools which computes Newey-West
covariance.

Also includes substantial improvements to tsatools, including numerous
bug fixes.   The code that handled recarrays has been improved to now
handle pandas dataframes.  Numerous doc strings where improved.  Test
coverage was also substantially increased.