Replace travis-ci badge with maintenance badge

Signed-off-by: Matthias Beyer <[email protected]>

Author: matthiasbeyer

Cargo.toml

@@ -11,7 +11,7 @@ categories = ["config"]
 license = "MIT/Apache-2.0"
 
 [badges]
-travis-ci = { repository = "mehcode/config-rs" }
+maintenance = { status = "actively-developed" }
 
 [features]
 default = ["toml", "json", "yaml", "hjson", "ini"]