fixed missing whitespace in Pajek writer when the ID attribute was numeric
Merge branch 'develop' of github.com:igraph/igraph into develop
fixed a bug that caused igraph_read_graph_gml to crash when the ID attribute was non-numeric
Python: added Vertex.graph and Edge.graph attributes, thanks to Bradford Boyle
Fixed issue #500, potential segfault (in R) if the two graphs in BLISS differ in the number of vertices or edges.
Merge branch 'develop' of github.com:igraph/igraph into develop
R: rewrote test cases using the testthat package.

Conflicts:
	interfaces/R/tests/bug-1073705-indexing.Rout.save
	interfaces/R/tests/get.shortest.paths.R
	interfaces/R/tests/get.shortest.paths.Rout.save
	interfaces/R/tests/leading.eigenvector.community.R
	interfaces/R/tests/leading.eigenvector.community.Rout.save
	interfaces/R/tests/modularity.matrix.Rout.save
	interfaces/R/tests/pajek.Rout.save
R: put tests in the package, and provide a function to run them. Closes issue #485.
R: move remaining test cases into the package.
Fix dyad census instability, sometimes incorrect results were reported. Fixes issue #496.

Conflicts:
	src/motifs.c
Dyad census detects integer overflow now and gives a warning. Fixes issue #497.
R: fixed a typo in the manual. Thanks to Stephen Haptonstahl for reporting it, see issue #503.
R: add.edges does not allow now zeros in the vertex set. Fixes issue #503, thanks to Stephen Haptonstahl for reporting it.
some C99 quirks fixed in lad.c; more to come
cleaned up igraph_i_lad_updateMatching as well
Updated ignore file.
fixed a memory leak in igraph_get_shortest_paths2.c
more fixes to the LAD isomorphism algorithm to make it C89-compliant
Remove AM_EXTRA_RECURSIVE_TARGETS from configure.ac, it requires a recent version of automake. Fixes issue #499.
Added bench.h and a simple benchmark for transitivity.