Update erlexec dependency to allow version 2.x

[weisslj]

exexec currently depends on erlexec ~> 1.10, but erlexec is currently at version 2.0.2, https://hex.pm/packages/erlexec; @ericentin maybe you could relax the dependency to allow erlexec 2.x (so it is compatible)? That would be great!

[weisslj]

@ericentin any update? We are forced to fork exexec or to use erlexec directly otherwise.

[almirsarajcic]

I have the same issue, hence #16.