Auto merge of #4431 - vignesh-sankaran:maintenance-badge-docs, r=alexcrichton

Add maintenance badge docs

Pending merging of [this PR for crates.io](rust-lang/crates.io#952). This should close off [#704 on crates.io](rust-lang/crates.io#704). I've also updated the badge metadata docs and reordered the fields into groups by build, code coverage, and maintenance.

So I've decided to put the list of possible badge options in the documentation, we'll have to find another place to put more detailed descriptions of the available maintenance badges.

Author: bors

src/doc/manifest.md

@@ -175,31 +175,28 @@ license = "..."
 # (similar to the readme key).
 license-file = "..."
 
-# Optional specification of badges to be displayed on crates.io. The badges
-# currently available are Travis CI, Appveyor, and GitLab latest build status,
-# specified using the following parameters:
+# Optional specification of badges to be displayed on crates.io. The badges 
+# pertaining to build status that are currently available are Appveyor, CircleCI,
+# GitLab, and TravisCI. Available badges pertaining to code test coverage are
+# Codecov and Coveralls. There are also maintenance-related badges which state
+# the issue resolution time, percent of open issues, and future maintenance
+# intentions.
 [badges]
 
-# Travis CI: `repository` in format "<user>/<project>" is required.
-# `branch` is optional; default is `master`
-travis-ci = { repository = "...", branch = "master" }
-
 # Appveyor: `repository` is required. `branch` is optional; default is `master`
 # `service` is optional; valid values are `github` (default), `bitbucket`, and
 # `gitlab`.
 appveyor = { repository = "...", branch = "master", service = "github" }
 
-# GitLab: `repository` is required. `branch` is optional; default is `master`
-gitlab = { repository = "...", branch = "master" }
-
 # Circle CI: `repository` is required. `branch` is optiona; default is `master`
 circle-ci = { repository = "...", branch = "master" }
 
-# Is it maintained resolution time: `repository` is required.
-is-it-maintained-issue-resolution = { repository = "..." }
+# GitLab: `repository` is required. `branch` is optional; default is `master`
+gitlab = { repository = "...", branch = "master" }
 
-# Is it maintained percentage of open issues: `repository` is required.
-is-it-maintained-open-issues = { repository = "..." }
+# Travis CI: `repository` in format "<user>/<project>" is required.
+# `branch` is optional; default is `master`
+travis-ci = { repository = "...", branch = "master" }
 
 # Codecov: `repository` is required. `branch` is optional; default is `master`
 # `service` is optional; valid values are `github` (default), `bitbucket`, and
@@ -209,6 +206,18 @@ codecov = { repository = "...", branch = "master", service = "github" }
 # Coveralls: `repository` is required. `branch` is optional; default is `master`
 # `service` is optional; valid values are `github` (default) and `bitbucket`.
 coveralls = { repository = "...", branch = "master", service = "github" }
+
+# Is it maintained resolution time: `repository` is required.
+is-it-maintained-issue-resolution = { repository = "..." }
+
+# Is it maintained percentage of open issues: `repository` is required.
+is-it-maintained-open-issues = { repository = "..." }
+
+# Maintenance: `status` is required Available options are `actively-developed`,
+# `passively-maintained`, `as-is`, `none`, `experimental`, `looking-for-maintainer`
+# and `deprecated`.
+maintenance = { status = "none" }
+
 ```
 
 The [crates.io](https://crates.io) registry will render the description, display