BUG: Make sure it's float division
BUG: Fix centered_tss for weighted regression
ENH: Always convert scalar weight to array
TST: Cleanup docstrings. Add WLS tests. Remove WLS_GLS comparison test.
TST: Full test for WLS
BUG: Fix likelihood for WLS.
DOC: Remove remark about GLS
REF: Remove impossible case from logic
STY: Remove commented out code
DOC: Some cleanup
Merge pull request #504 from jseabold/fix-weights

Fix weights. Closes #501.
ENH: Protect numdifftools import. Closes #45
Merge pull request #507 from jseabold/fix-45

ENH: Protect numdifftools import. Closes #45
DOC: realdpi is disposable personal income. Closes #394.
Merge pull request #510 from jseabold/macro-docs

DOC: realdpi is disposable personal income. Closes #394.
DOC: Add ARIMA to docs
Merge pull request #509 from jseabold/arima-docs

DOC: Add ARIMA to docs
ENH: Avoid taking cholesky decomposition of diagonal matrix
Merge pull request #508 from jseabold/cholesky-diag

ENH: Avoid taking cholesky decomposition of diagonal matrix. Closes #488.
DOC: Fix bullet list typo