Setup script (python) lacks verification for hexdump installation

While running setup script (python proxy), I've got following error message:
```
Do you want to set secret manually or shall I create a random secret?
   1) Manually enter a secret
   2) Create a random secret
Please select one [1-2]: 2
MTProtoProxyInstall.sh: line 571: hexdump: command not found
OK I created one:
```