Merge pull request #51 from jread-usgs/master

as CRAN issue fixes
Added check for z.mix because it's a major pitfall.
Minor documentation change.
wrote documentation for metab.mle; reuse eqs

the equations in the file are really solid, and can be recycled for metab.bayesian, metab.kalman, and somewhat for others. Includes both Latex and Ascii eqn and deqn. Good details section, right units, etc. Less focus on the actual coding aspect of the documentation, and more on the statistics.
add to .Rd mle & Kalman, fix browser(), fix z.mix error msg
added -wtr error msg to metab.xxx functs, similar to z.mix msg
standardized @return across models (data.frame portion, not attr's)
tried to standardize interpretation of ... across metab.xxx
Fixed non-ascii characters.
Added package documentation and Roxy.
fixed typo in o2.at.sat
subsetted example data.
Removed buggy date2doy function and replaced with better method.
Made error messages more useful.
Changed example used to fit new, shorter dataset.
typo fix.
Fixed version of addNAs and byeShort to reduce complexity and improve short timestep handling.
Reverted my earlier changes to this.
Typo Fix
Cut down TB data to manageable size.