* Add checksum to install script
This will allow someone to check if Babashka is correctly downloaded,
e.g.:
```
$ ./install --dir /tmp --checksum 3cb19f158b9f1655e0165b6c4067d35faaa05882bbdb230616c91085b02b5bf4
Downloading https://github.com/babashka/babashka/releases/download/v0.4.1/babashka-0.4.1-linux-amd64.tar.gz to /tmp
Failed checksum on babashka-0.4.1-linux-amd64.tar.gz
Got: 3cb19f158b9f1655e0165b6c4067d35faaa05882bbdb230616c91085b02b5bf3
Expected: 3cb19f158b9f1655e0165b6c4067d35faaa05882bbdb230616c91085b02b5bf4
```
There is no check by default. This makes this change backwards
compatible (e.g.: if the machine doesn't have sha256sum, this change
will not break installation).
* Add --static to install script
This will allow installation of static instead of dynamically binaries
on Linux.
* Add checksum to print_help
* Add check that --checksum and --options should be provided together
