dsm news!

# 2.2.5
 * dsm.var.prop will now throw an error if there is no detection function in the dsm that it's trying to calculate the variance for (thanks to Adrián Schiavini for finding this)
 * variance/CV plotting threw an error when no detection function was supplied but observation=TRUE. Now error is sidestepped (again, thanks to Adrián Schiavini for finding this).

# 2.2.4
 * changed stop() to warning() when data not in the detection function are included in the observation data frame, as they are automatically excluded later, bug found by Eric Rexstad and Anna Cucknell

# 2.2.3
 * moving block boostrap was using observed abundances as the residuals and therefore gave wrong answers (Eric Rexstad found this bug)

# 2.2.2
 * version number reporting now works (Len Thomas found this bug)
 * more documentation
 * by default density and presence models are now weighted by area of each segment

# 2.2.1
 * switch over to new testthat spec
 * added new response variables (Dhat, density.est, count, n), suggestion from Len Thomas

# 2.1.4
 * check that all observed distances are within width will now throw an error

# 2.1.3
  * CRAN-compatibility fixes

# 2.1.2
  * updates to dsm.cor
  * more unified plotting
  * variance estimation tweaks for non-dsm models

# 2.0.6
  * removed warning about if() comparison length in make.soapgrid need to pass bnd as a list()
  * dsm.cor now handles gamm objects
  * dsm.cor allows one to check residual autocorrelation in your models
  * presence/absence data now no longer needs a dummy detection function object

# 2.0.5
  * started NEWS file
  * fixed bug where dsm.var.gam() didn't return predictions so plotting the result would fail
  * silly typo in docs
  * check if we're using mgcv version >= 1.7-24 for GAMM fitting and warn if not

