Fix shard connection

Fixes shard connections by removing the Default implementation for
Shards.

This was because when instantiating a Shard, `..Default::default()`
syntax was used, which calls the `Default` implementation of the struct
and moves the necessary values over to the overlying instantiation.

When using `..Default::default()` syntax, all values in the Default
implementation are instantiated, even ones that could be deemed
unnecessary.

For example, in the following sample code:

```rust
struct Foo {
    x: bool,
    y: bool,
}

impl Default for Foo {
    fn default() -> Self {
        Self {
            x: true,
            y: true,
        }
    }
}

// ...
let foo = Foo {
    x: false,
    ..Default::default()
};
```

`Foo::x` will still be instantiated in the Default implementation
despite a value being set in the user's instantiation of Foo.

This causes WebSocket client instantiation to be invalid in the Default
instantiation, because the WebSocket instantiated has no base URL,
causing an error to be returned.

This commit resolves this issue by simply not having a Default
implementation - due to the fact that a default implementation will
never be valid and successful - and instead set all values in
`Shard::new`.

Notes: This issue surfaced with commit
fcc4e2ce2e523248ed33c9f4853d3485cbc9b6e6 (PR #195).

Closes #203.

0 files changed, 0 insertions, 0 deletions