Map/Unmap buffer issue testing
Initial update for NAN suport
ported to NAN, except async code in event, program, webcl
ported to NAN without async callback support
updated CL event callback support
code cleanup
NAN 0.8.0 required
added async callback support
Merge branch 'feature/nan_support' into develop
updated readme for NAN requirement
Merge branch 'release/v0.8.0'