Use os.platform instead of command detection

[toddpi314]

find on Windows vs *nix has different behavior. Blocks like https://github.com/Chrisvin/EasyAndroidEmulator/blob/master/src/index.js#L137-L145 will map to the find tool on *nix and fail, since the piped system image data isn't a file system handle.

Consider switching to using os.platform and favoring grep for *nix

[Chrisvin]

Thanks for bringing this to my attention. Will check on this.