DOC: Fix section titles
Merge pull request #801 from jseabold/docs-cleanup

DOC: Fix ANOVA section titles
TST: Test SVD convergence failure due to bad start params.

TST: Add test
ENH: Check for bad values from start_params for ARMA. Closes #675. Closes #15.

BUG: Include all AR params
STY: Remove comment
BUG: Use correct definition for root checking.
Merge pull request #803 from jseabold/fix-arima-error-msg

ENH: Fix arima error message for bad start_params
ENH: Import formula.api in statsmodels.api namespace.
Merge pull request #806 from jseabold/formula-api

ENH: Import formula.api in statsmodels.api namespace. Closes #804.