REF/STY: Standardize variable names. Pep-8. Docs cleanup
ENH: Import ArmaProcess and arma_generate_sample to api.
REF: Remove unused estimation class.
STY/REF: Pep-8. Fix broken variable names. Remove imports.
REF: Don't need to set attributes of super class
REF: Update for size -> nsample consistency rename.
DOC: Reverse poly coef example
Merge pull request #1426 from jseabold/arma-process-cleanup

ENH: Import arima_process stuff into tsa.api