Macros for container literals with specific type.
```
#[macro_use] extern crate maplit;
# fn main() {
let map = hashmap!{
"a" => 1,
"b" => 2,
};
# }
```
The **maplit** crate uses `=>` syntax for the mapping macros. It is
not possible to use `:` as separator due to syntactic restrictions in
regular `macro_rules!` macros.
Note that rust macros are flexible in which brackets you use for the invocation.
You can use them as `hashmap!{}` or `hashmap![]` or `hashmap!()`.
This crate suggests `{}` as the convention for the map & set macros,
it matches their `Debug` output.
Generic container macros already exist elsewhere, so those are not provided
here at the moment.