Improved read/write performance

- treat binary-data directly
- read from fd up to 64kB at a time
Improved read timeout (w32)
Comment out unused functions
Remove unused functions
Merge pull request #161 from Shougo/improve-readwrite

Improve read/write performance
Improved read_line() performance
Improved s:system() timeout
Clean-up interrupted process
Improve documentation.

Write:

1. File object
1. Socket object
1. Process object
Merge pull request #163 from Shougo/improve-system

Improve s:system()
Merge pull request #162 from Shougo/improve-read_line

Improve read_line() performance
Merge pull request #164 from kamichidu/pr

Improve documentation.
Fixed vp_file_open() flags
Fixed vp_kill; in case a child process has delayed
Merge pull request #167 from ichizok/fix-vp_kill

Fix vp_kill
Fixed vp_kill; kill pgid only if pid == pgid
Merge pull request #170 from ichizok/fix-vp_kill

Fix vp_kill
Update documentation
Fix example
[WIP] Improved portability to AIX, HP-UX