First attempt at adding some support for IRIS

This is a pretty basic attempt, it adds a function that converts a
SJI cube into a MapCube, by replicating the header.

Also added a 'blank' map source for this type of image.
Add IRIS to map sources __init__
Change class doc string!
Add IRIS to changelog
Change hdu[0] to hdu for optional indexing
Merge pull request #8 from CyclingNinja/iris

Change hdu[0] to hdu for optional indexing
Modify GenericMap.rotate to allow rmatrix as argument.

Allow rotate() to accept either angle or a linear transform rotation
matrix. This is to facilitate WCS pci_j matirx rotation.
Add method to align IRISMap by rotation from header
Merge pull request #9 from CyclingNinja/iris

Iris
First attempt at adding some support for IRIS

This is a pretty basic attempt, it adds a function that converts a
SJI cube into a MapCube, by replicating the header.

Also added a 'blank' map source for this type of image.
Add IRIS to map sources __init__
Change class doc string!
Add IRIS to changelog
Change hdu[0] to hdu for optional indexing
Modify GenericMap.rotate to allow rmatrix as argument.

Allow rotate() to accept either angle or a linear transform rotation
matrix. This is to facilitate WCS pci_j matirx rotation.
Add method to align IRISMap by rotation from header
Major refactor of the docs, phase 1

Move to use the astropy affiliated package template for the docs,
started on a proper api doc using astropy and fixed some docstrings
add back in other doc pages
one warning in guide and other tweaks
re-add examples