toy-graph v0.4

this version needs much code optimization.

1. add thread pool for computation.

toy-graph v0.3

1. add a thread-safe queue.
2. add async_reader

toy-graph v0.2

1. modify design of reader, commandline, graph, etc...
2. make api more clean and simple.
3. add convert_to_binary tool.
4. fix bugs.
5. add pagerank example and shell script to test.

toy-graph v0.1

this version only supports single machine single thread computation, need a lot of modification.

1. add gtest, commandline, logging.
2. fix bugs.