new GalSim version: v0.4

[Rachel Mandelbaum]

We are pleased to announce a new tagged version of GalSim, v0.4, which
can be obtained from our GitHub page,
https://github.com/GalSim-developers/GalSim/
or for Mac users, from homebrew and macports (see detailed
instructions in
https://github.com/GalSim-developers/GalSim/blob/master/INSTALL.md ).
Below is a list of changes from the previous version, reproduced from
CHANGELOG.md:

* When making GSObjects out of real images that have noise, it is
possible to pad those images with a noise field (either correlated or
uncorrelated) so that there is not an abrupt change of properties in
the noise field when crossing the border into the padding region.
(Issue #238)

* Option for shears from a power spectrum: use a tabulated P(k),
either input as arrays or read in from a file, for example from a
cosmological shear power spectrum calculator. Also, the PowerSpectrum
class now properly handles conversions between different units for
P(k) and the galaxy positions at which we are calculating shear.
Finally, an important bug in how the shears were generated from the
power spectrum (which resulted in issues with overall normalization)
was fixed. (Issue #305)

* An optimization of the InterpolatedImage constructor. (Issue #305)

* A work-around for a pyfits bug that made our Rice-compressed output
files (using pyfits) unreadable by ds9. (Issue #305)

* There is now a python interface to C++ tables that can be used for
interpolation in a more general context. (Issue #305)

* Added a DistDeviate class that generates pseudo-random numbers from
a user-defined probability distribution. (Issue #306)

* A free function added that gives the user quick access to the 2D
spatial correlation function of noise in HST COSMOS F814W weak lensing
science images (e.g. Leauthaud et al 2007). Calling
galsim.correlatednoise.get_COSMOS_CorrFunc(...) returns a correlation
function that shares all the methods of a galsim.ImageCorrFunc(), and
optional keyword inputs allow the point variance and physical scale of
the function to be set correctly. (Issue #345)

* Added an addNoiseSNR() method to Image classes that adds noise such
that the image has a specified signal-to-noise ratio. (Issue #349)

* Made a new Noise hierarchy, and moved CCDNoise to that rather than
have it be a BaseDeviate. There are also now GaussianNoise,
PoissonNoise, and DeviateNoise classes. (Issue #349)

* Small bug fix for multiple operations on GSObjects when drawing
images using photon shooting, which affects combinations like shifting
and shearing. (Issue #359)

* New demo11 script that includes getting PowerSpectrum shears from a
file, uses an InterpolatedImage for the PSF, uses DistDeviate
(RandomDistribution in the config) for the sizes, and applies
correlated noise such as found in COSMOS to the output image. (Issues
#305, #306, #345)

* Minor bug fix for correct directory handling in the executable
versions of the demo scripts, i.e. those generated in the
bin/subdirectory using scons examples. (Issue #345)