Make DFS tests pass on 32-bit machines.

simple_inclist uses Ints for vertices; on 32-bit machines, Int == Int32.
But test/dfs.jl hard-coded the use of Int64s for test data, which caused
type errors.
Merge pull request #66 from pozorvlak/32bit_dfs_test

Make DFS tests pass on 32-bit machines.
fixed multivecs call in simple_adjlist construction for adjacency matrix
Merge pull request #72 from uriahjb/master

fixed multivecs call in simple_adjlist construction for adjacency matrix
IOString -> IOBuffer rename from Base Julia

Fix #74
Merge pull request #75 from ivarne/patch-1

IOString -> IOBuffer rename from Base Julia
Update cliques to initialize pivotdonenbrs

pivotdonenbrs is not in a high enough scope to be seen between when it is defined and when it is referenced the second time.  Without this change I get:

```
ERROR: pivotdonenbrs not defined
 in maximal_cliques at /home/user/.julia/v0.3/Graphs/src/cliques.jl:125
while loading solver.jl, in expression starting on line 38
```