Upgrade to petgraph 0.6

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "tree_magic_mini"
-version = "3.0.1"
+version = "3.0.2"
 authors = [
     "Matt Brubeck <mbrubeck@limpet.net>",
     "Allison Hancock <aahancoc@umich.edu>",
@@ -15,23 +15,19 @@ exclude = ["tests/*", "benches/*/"]
 edition = "2018"
 
 [dependencies]
-petgraph = "^0.5"
+petgraph = "0.6.0"
 nom = "7.0"
-lazy_static = "^1.4"
-fnv = "^1"
-bytecount = "^0.6"
-once_cell = "^1"
-tree_magic_db = { version = "3", path = "./magic_db" , optional = true }
+lazy_static = "1.4"
+fnv = "1.0"
+bytecount = "0.6.0"
+once_cell = "1.0"
+tree_magic_db = { version = "3.0", path = "./magic_db" , optional = true }
 
 [features]
 with-gpl-data = ["tree_magic_db"]
 
 [dev-dependencies]
-bencher = "^0.1"
-
-[lib]
-crate-type = ["lib"]
-path = "src/lib.rs"
+bencher = "0.1.0"
 
 [workspace]
 members = ["magic_db"]