Added implementation of LoadEdgeListNet
Added SaveEdgeListNet method
Added more commenting to file
Replace edge attributes with default value with - in files
Load/SaveEdgeListNet now supports node attributes
Merge remote-tracking branch 'upstream/master'

Conflicts:
	snap-core/network.h
Added comments for methods in gio.cpp
Now ignores blank lines
END sentinel line optional for LoadEdgeListNet
Merge pull request #53 from sramas15/master

Implement LoadEdgeListNet and SaveEdgeListNet