fix a bug related to options.length in ReadStream;

also clearing out the code to make the logic obvious
add keepalive and nodelay

Credit: Deniz Piri
https://github.com/luvit/luvit/pull/269
add a test case for cf8fec627
add changelog for 0.8.2
Merge pull request #469 from luvit/songgao/fix_fs_readstream_length

fix a bug related to options.length in ReadStream
Merge pull request #471 from luvit/fixes/no_delay_keepalive

add keepalive and nodelay