Update to canonical eip-X format (#2734)
It appears that the format `EIP-X` is preferred to `EIPX`:
```console
$ grep "EIP-[0-9]+" * | wc -l
373
$ grep "EIP[0-9]+" * | wc -l
118
```
Also note that several of the `EIPX` references are coming from `index.html` and `EIPS/eip-1.md`.
```console
$ grep "EIP[0-9]+" index.html | wc -l
4
$ grep "EIP[0-9]+" EIPS/eip-1.md | wc -l
13
```
I have updated `index.html` and `eip-1` accordingly.
GitHub Diff