update plugin version and contributors list
fix project's URL
set target Cytoscape version to 2.8.2 and update maven repositories location
let maven generate MANIFEST.MF
don't require specific maven-assembly-plugin version
simplify Writer methods by making XML document a field of the class
write GraphML namespace and comment about the plugin
write attribute definitions before the graph
correctly write object type for attribute definition
write network-level attributes
generate unique internal attribute IDs
extract attribute definition and appending methods
if XML element is given, write it to <data/> directly
provide current network view for GraphMLWriter
convert NodeView properties into yWorks nodegraphics attribute
convert EdgeView properties into yWorks edgegraphics attribute
use FileOutputStream instead of FileWriter

that way correct UTF8 characters are being written
(but no UTF8 prefix in the beginning)
set 'packaging' as the default goal
[*] refactor attributes parsing

- allow overlapping IDs for attributes of different scopes (nodes, edges)
- support int, float, boolean attributes
- make sure the whole attribute data is read