Make pub_semver a normal dep (issue #275)

Author: ochafik

pkg/dev_compiler/pubspec.yaml

@@ -13,6 +13,7 @@ dependencies:
   html: ^0.12.0
   logging: ">=0.9.2 <0.12.0"
   path: ^1.3.0
+  pub_semver: ^1.1.0
   shelf: ">=0.5.6 <0.7.0"
   shelf_static: ^0.2.1
   source_maps: ^0.10.0
@@ -23,7 +24,6 @@ dev_dependencies:
   # the same way. This is because any change in dart_style, even non-breaking
   # changes, may change the output format.
   dart_style: 0.2.0
-  pub_semver: ^1.1.0
   test: ^0.12.0
 environment:
   sdk: ">=1.12.0-dev.1.1 <2.0.0"