Flashx

Fix some bugs.

This contains some small updates:
1. disable FlashEigen by default.
2. create utility tools: el2fg, fg2fm.

Fix some minor bugs when stxxl library doesn't exist

The main improvement in this release is to load a graph to FlashGraphR more easily. It can now load a graph in edge list format and adjacency list format from Linux filesystem directly. It can also load a graph from iGraph directly.

This release provides the programming framework for users to implement graph algorithms for processing massive graphs. It also provides some graph algorithm implementation such as
- weakly connected components,
- strongly connected components,
- PageRank,
- triangle counting,
- diameter estimation,
- Kcore,
- clustering coefficient,
- spectral clustering,
...

It also provides an eigensolver and SVD.

The release also provides R bindings, so that R users can invoke the existing graph implementation in FlashGraph to process massive graphs.