fix local nxm search

Clear code and add clarifications (#22)

* redudant AddVertex()

* merge relaxation and actual dijkstra

* count edges and shourtcuts on a fly + add getters

* redudant 'IsShortcut'

* organize heaps

* shorten

* rev names

* mv incident

* redudant NewVertex

* decrease vertex fields num

* rm heaps from graph

* name

* redudant nodeOrdering?

* run fmt

* pointer to incident edge

* rename

* merge relaxation and bi-dir search

* order could be int64, clarification about contraction id

* consider Goish loops

* continue goish loops

* merge checkID

* com

* clarify previousSourceID

* comment section

* comment section

* comment section

defer close + naming

update epoxrt functions

update shortcut getter

two new getters

num of shortcut increased (again)

Merge pull request #16 from LdDl/new-export-import

replace int64 with ContractionPath + eliminate duplicates from contra…

Merge pull request #15 from LdDl/new-export-import

Improve export/import

Merge pull request #9 from LdDl/isochrones

fill readme/implement+test