Tag Graphs v0.4.2

Graphs v.0.4.1 [no longer works on Julia 0.3](https://github.com/JuliaLang/Graphs.jl/issues/79) since it makes use of deprecated Julia features that have now been removed. This release

 - removes the use of such abandoned features, making the build pass again
 - fixes several other bugs
 - adds more documentation
 - adds an algorithm to find the maximal cliques in a graph
 - adds the A* shortest-path algorithm.

Contributors: @lindahua, @pozorvlak, @mlubin, @david-crespo, @ivarne, @daviddelaat, @GlenHertz, @aviks, @uriahjb,