FIX: Allow as_grey on RGBA images.
FIX: Ignore (drop) alpha channel if it exists, following skimage.
Merge pull request #117 from danielballan/fix-as-gray-with-alpha

FIX : Allow as_grey on RGBA images.
ENH: By default, compute a lossless bitrate.
Merge pull request #115 from danielballan/estimate-bitrate

ENH: By default, compute a lossless bitrate.
ENH : creating a Frame from a Frame propagates md

When making a Frame from a Frame, propagate the metadata
and frame number, overriding from the kwargs.
Merge pull request #123 from tacaswell/frame_copy_constructor

ENH : creating a Frame from a Frame propagates md
ENH: Convert multichannel to RGB

- adds function `to_rgb` that converts a multichannel N-dimensional
image to RGB image
- implements this in the `_repr_html_` function
Minor adaptations, docstrings
Removed wavelength to rgb

In stead of wavelength -> rgb, use matplotlib color -> rgb conversion.
Wavelength conversion code had unclear licensing.
Metadata tag 'color' is used, changed defaults

- default colors are now cyan/green/magenta/red
- color metadata is checked and used
Made _monochannel_to_rgb global
Changes after line notes

- added clipping step, when colors overlap too much, renormalizing would
reduce the luminosity of the channels. When clipping needs to be
avoided, the user can specify his own RGB values (see docstring)
- when normalize == True, also monochannel images are normalized
- moved import ColorConverter to module level
- defaults colors are now directly rgb to circumvent ColorConverter
- more efficient _monochannel_to_rgb
Removed unnecessary -> int conversion

- calculations are in floats, and only when normalize = True the
datatype is converted to np.uint8 at the end
- mistake in _repr_html_ for display of 2D multichannel
Cleanup

- made PEP8 compatible
- `colors == None` becomes `colors is None`
- replaced undefined variable `i` with `0`
Merge pull request #120 from caspervdw/display-multichannel

Display multichannel image
Wrapper for python-bioformats

Required are:
Python-bioformats: https://github.com/CellProfiler/python-bioformats
Python-javabridge: https://github.com/CellProfiler/python-javabridge
Add bioformats reader to api.py
Minor changes
Load metadata at get_frame instead of initialize

This saves a lot of initial loading time, only loads metadata of
required frames. Also stores last frame (may be useful to arrange this
at frame.py level?)

Added omexml metadata importer, this is demanding for large files and
may require a higher java heap space.

Added direct use of the java-wrapped MetadataRetrieve routines
(mdstr/mdint/mdfloat). The latter are much faster but more information
is obtained with omexml. The java command including parameters are
passed as string. See this link for the full list of options:

http://downloads.openmicroscopy.org/bio-formats/5.0.5/api/loci/formats/meta/MetadataRetrieve.html