The gexfparser is now able to parse temporal graph

In stead of parsing all edges in the gexf file, it is now able to parse only the
edges in a specified timestep or range of timesteps. These can be fed to the
spring embedding while keeping the vertices constant.
Cleaning main.
Added a new reference file for output

This file is the output of running 100 iterations on the lanes.gexf file with
Force Atlas 2. In this run, only the edges (and vertices) that are valid at
timestep 0 are taken into account. This results in 332 edges.
Copying the vertex IDs to the output array.
Merge branch 'master' into parse-temporal

Conflicts:
	src/main.c