Parses simple text format into a HashMap.

The keys and values are both strings and are separated by whitespace. The value is allowed to contain whitespaces.

Example

Key-Value-File:

key1 value1
key2 value2
key3 value3

The result would be a HashMap like this:

let mut map = HashMap::new();
map.insert("key1".to_string(), "value1".to_string());
map.insert("key2".to_string(), "value2".to_string());
map.insert("key3".to_string(), "value3".to_string());
assert_eq!(map, file_to_key_value_map(path));