Ensure compatiblity with /lib/exporter.rb in MapKnitter

[jywarren]

There've been minimal changes to the library itself, but 2 to watch out for are:

1. changes of object.lat to object[:lat] everywhere, similar for [:nodes_array]
2. change of image.url to string image_url in run_export

Here's a diff of the file from the original copy in from MapKnitter:

e140646...bf375b6#diff-174ec2997e5f3c6e51179e598ab47217R314

We should be able to get MapKnitter to install this gem and still pass it's test at /tests/unit/exporter_test.rb if we respect these changes.

[jywarren]

This should use usable as in the tests, after including the gem, and then:

mapknitter-exporter/test/exporter_test.rb

Line 2 in bf375b6

require "./lib/mapknitterExporter"

Although I think it'll be require 'mapknitterExporter' -- probably!

[jywarren]

Also we need to pass in this nice MockExport object:

mapknitter-exporter/test/exporter_test.rb

Lines 125 to 133 in bf375b6

	class MockExport
	attr_accessor :status, :tms, :geotiff, :zip, :jpg
	def save
	puts "saved"
	end
	end

[jywarren]

MockExport is what will write the status.json files, whenever we save!

[jywarren]

Following publiclab/mapknitter#364 (comment)

[jywarren]

And we'll have to refactor from the simplified version here: #6 !!

[jywarren]

After refactoring "root" we should be ok to do this.

[jywarren]

OK, #530 brings mapknitter up to date with the latest of this gem!

[jywarren]

er, publiclab/mapknitter#530