Merge pull request #1 from ryaninhust/master

Update
Merge branch 'master' of https://github.com/ryaninhust/sampling
Merge branch 'master' of https://github.com/ryaninhust/sampling
Merge branch 'master' of https://github.com/ryaninhust/sampling
[Fix] Big Fix to kill bug
Merge branch 'master' of https://github.com/ryaninhust/sampling
Merge branch 'master' of https://github.com/ryaninhust/sampling
[Add] add algorithm random jump, forest fire, snow ball
Merge pull request #4 from Hyiiego/master

Add algorithms
[Milestone] Merge Huangyi code
[Fix] modify forest fire and snow ball
Merge pull request #5 from Hyiiego/master

[Fix] modify forest fire and snow ball
[Fix] if unvisit_edge list is empty, just continue
Merge pull request #6 from Hyiiego/master

[Fix] if unvisit_edge list is empty, just continue
[Fix] fix start_seeds bug
Merge pull request #7 from Hyiiego/master

[Fix] fix start_seeds bug
Merge branch 'master' of https://github.com/ryaninhust/sampling
remove read_nodes
sampling algorithm
remove original sample network