rename epoch to edition

[klnusbaum]

Per issue #5214 let's rename all instances of epoch to Edition

[Manishearth]

r? @alexcrichton

[Manishearth]

$ cargo fmt -- --write-mode diff
Diff in /home/travis/build/rust-lang/cargo/src/cargo/util/toml/mod.rs at line 14:
 ⏎
 use core::{GitReference, PackageIdSpec, Profiles, SourceId, WorkspaceConfig, WorkspaceRootConfig};⏎
 use core::{Dependency, Manifest, PackageId, Summary, Target};⏎
-use core::{EitherManifest, Edition, Feature, Features, VirtualManifest};⏎
+use core::{Edition, EitherManifest, Feature, Features, VirtualManifest};⏎
 use core::dependency::{Kind, Platform};⏎
 use core::manifest::{LibKind, Lto, ManifestMetadata, Profile};⏎
 use sources::CRATES_IO;⏎

[alexcrichton]

@bors: r+

Thanks!

[bors]

📌 Commit 3bbe93c has been approved by alexcrichton

[bors]

⌛ Testing commit 3bbe93c with merge 551f6f3...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: alexcrichton
Pushing 551f6f3 to master...