Merge pull request #63 from robjhyndman/enhancement

fixed a bug in getResponse.lm
Changed some "large numbers" from 1e8 and 1e12 to Inf/R_PosInf. This was causing problems if the series had very large numbers.
Updated Changelog with Christoph's fix for large observations
Protect if ncol(xreg) == 1 and length(nmxreg) > 1. Closes #65.
Merge pull request #66 from jseabold/fix-65

Protect if ncol(xreg) == 1 and length(nmxreg) > 1. Closes #65.
ets with constant data, and arima.errors improved
Merge branch 'master' of http://github.com/robjhyndman/forecast

* 'master' of http://github.com/robjhyndman/forecast:
  Protect if ncol(xreg) == 1 and length(nmxreg) > 1. Closes #65.
Release v5.4 for CRAN
Made all tests conditional on fpp being available
Fixed problem in checking unit roots of an ARIMA model when all coefficients equal to zero
Improved documentation for croston()
Changed initialization of multiplicative seasonality in ETS models to avoid negative values
Added forecastfunction argument to forecast.stl and stlf
Improved forecast.ar to be more likely to work when embedded.
Added stlm() and forecast.stlm()
Modified stlm() so that it takes a ts object rather than an stl object
Improved handling of some ARIMA models
further update fourier/fourierf
resolve merge conflicts