Show error context for config file

[yantonov]

Right now, if config file is broken this line will be outputed: "Error while parsing config file"

In particular:

thread 'main' panicked at 'called Result::unwrap() on an Err value: "Error while parsing config file"', src/main.rs:34:10
note: run with RUST_BACKTRACE=1 environment variable to display a backtrace

Error context is ommited, this should be fixed.