update webfinger

as requested in https://github.com/Plume-org/webfinger/issues/8
and provided in https://github.com/Plume-org/webfinger/pull/9

```
meena@76ix ~/s/a/plume (go/async) [101]> cargo update --package webfinger
    Updating crates.io index
    Updating git repository `https://github.com/Plume-org/webfinger`
    Removing bytes v0.4.12
    Removing cookie v0.12.0
    Removing cookie_store v0.7.0
    Removing crossbeam-deque v0.7.2
    Removing crossbeam-epoch v0.8.0
    Removing crossbeam-queue v0.1.2
    Removing crossbeam-utils v0.7.0
    Removing h2 v0.1.26
    Removing http v0.1.21
    Removing http-body v0.1.0
    Removing hyper v0.12.35
    Removing hyper-tls v0.3.2
    Removing publicsuffix v1.5.4
    Removing reqwest v0.9.24
    Removing serde_urlencoded v0.5.5
    Removing string v0.2.1
    Removing tokio v0.1.22
    Removing tokio-buf v0.1.1
    Removing tokio-current-thread v0.1.6
    Removing tokio-executor v0.1.9
    Removing tokio-io v0.1.12
    Removing tokio-reactor v0.1.11
    Removing tokio-sync v0.1.7
    Removing tokio-tcp v0.1.3
    Removing tokio-threadpool v0.1.17
    Removing tokio-timer v0.2.12
    Removing try_from v0.3.2
    Removing want v0.2.0
      Adding webfinger v0.5.0 (https://github.com/Plume-org/webfinger?rev=update-deps#cdaab95e)
    Removing webfinger v0.5.0
meena@76ix ~/s/a/plume (go/async)>
```

plume-models/Cargo.toml

@@ -24,7 +24,7 @@ tantivy = "0.10.1"
 tokio = "0.2"
 url = "2.1"
 walkdir = "2.2"
-webfinger = "0.5"
+webfinger = { git = "https://github.com/Plume-org/webfinger", rev = "update-deps" }
 whatlang = "0.7.1"
 shrinkwraprs = "0.3"
 diesel-derive-newtype = "0.1.2"