Add options

[Leedehai]

I added some options to make it look nicer:

python python-readelf/readelf.py -h # of course you could give it executable permission by "chmod +x"
usage: readelf.py [-h] [-v] [-eh] [-ph] [-sh] [-it] [-st] [-ds] [-a] file

positional arguments:
  file                  path to the ELF file

optional arguments:
  -h, --help            show this help message and exit
  -v, --version         version info
  -eh, --elf-header     print ELF header
  -ph, --program-header
                        print program headers
  -sh, --section-header
                        print section headers
  -it, --interp         print interp, i.e. the dynamic loader (itself a shared
                        binary)
  -st, --symbol-table   print symbol table
  -ds, --dynamic-section
                        print dynamic section
  -a, --all             print all (default)

The dynamic loader itself is a shared binary, according to this article.