added es6 modules

I've tried comparing comparing the new G.js file with old one using http://prettydiff.com. This helps us to compare two JS files. Please have a look.

See merge request !1

Let's assume aggregate is sum(). Earlier, we had link = sum(source,
target). Now, we have link = sum(nodes were source & target match). This
is clearly much more useful, and more intuitive

test/lib/G.js isn't the ideal path for the output. Need to revamp this

Sometimes, links resolve partially to node objects. That is, some links
become node objects, some do not. Hence, check every link independently.

For example, if the URL is ?a=1&b=1 and we want to update it with
?a=2&b=3, updating 'a' but toggling 'b', then we can specify
mode='b=toggle'. This will only toggle 'b', not 'a', and result in the
URL ?a=2&b=1&b=3

This causes a problem when random numbers are used for sizes. The second
time the function is called, the values are different.