Merge pull request #14 from rpl-cmu/pin-version

Pin rust version

Cargo.toml

@@ -9,6 +9,7 @@ authors = ["Easton Potokar", "Taylor Pool"]
 repository = "https://github.com/rpl-cmu/factrs"
 keywords = ["nonlinear", "optimization", "robotics", "estimation", "SLAM"]
 categories = ["science::robotics", "mathematics"]
+rust-version = "1.81"
 
 [package.metadata.docs.rs]
 rustdoc-args = ["--html-in-header", "assets/katex-header.html"]