In theory, all panics after this should be bugs instead of normal
error conditions.
The error reporting may still need finetuning. For example, if the
hostname doesn't resolve you get a redundant traceback:
```
Error: error sending request for url (http://bad-hostname/): error trying to connect: dns error: failed to lookup address information: Name or service not known
Caused by:
0: error trying to connect: dns error: failed to lookup address information: Name or service not known
1: dns error: failed to lookup address information: Name or service not known
2: failed to lookup address information: Name or service not known
```
This commit also fixes all of the remaining Clippy warnings.
Resolves#14 (?)
