prevalence 0.4.0
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* new method `as.matrix` for objects of class `prev`
* add SE, SP to `truePrev` and `truePrevPools` output
* fixed some documentation typos
* updated website and email address
* updated Description field to fix CRAN note
prevalence 0.3.0
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* new function `truePrevMulti2`, implementing a covariance scheme for
estimating TP from AP obtained with multiple tests
* new function `define_prior2` to show the definition of the priors used
by `truePrevMulti2`
* definition of `x` in `truePrevMulti` is reversed; first element of `x` now
is the number of samples positive on all tests, last element of `x` is the
number of samples negative on all tests
* 'definition' functions renamed to `define_x` and `define_prior`
* functions `truePrev` and `truePrevPools` lost args `conf.level` and `plot`
* function `betaPERT` lost args `p` and `plot`
* print method for objects of class `prev` no longer shows percentages
* various code cleanups and small bug and typo fixes