Some minor notes
Add uts namespace related options
Rakefile: remove temp file
Improve --syscalls parser

The parser is rewritten and it is now:

- Allow filtering by arguments (SCMP_CMP), like:
  write[a=1],read[a!=0],foo[b&3=1,d>2] etc.
- Transparently handles the `execve` case:
  `--syscalls '!execve'` now works.
strconv: add to_bytes

to_bytes resolves things like "32K", "0.5mb", "1.2g"
Only root can set nice with a negative value
Improve help and README

- Rewrite print_help(). It now adapts to terminal width
- Explain new syscall filter with `--help-syscalls`
- Mention linux < 3.5 is unsafe in README
- Add "Output format" section to README