Bugs in 0.3.0

First bug patch PR to 0.3.0.

Thanks to @examon for finding these!

Three bugs:
Map() couldn't pass arguments to io.read_file, it does now.
CompositeMap's contour plotting is broken
you can now pass dict to Map and it will convert to a MapMeta.

@rhewett I messed with Map() take a look if you have 5? I am not sure it is the best way to do it.