give sessiongenerator a master context for easy cancelling
style: Stop -> Close() error for Closer interface

License: MIT
Signed-off-by: Brian Tiger Chow <brian@perfmode.com>
doc TODO

License: MIT
Signed-off-by: Brian Tiger Chow <brian@perfmode.com>
Merge pull request #448 from jbenet/fix/test-memory-leak

fix: memory leak in epic tests