Roll Observatory packages and add a roll script

packages/path/CHANGELOG.md

+## 1.3.6
+
+* Ensure that `path.toUri` preserves trailing slashes for relative paths.
+
+## 1.3.5
+
+* Added type annotations to top-level and static fields.
+
+## 1.3.4
+
+* Fix dev_compiler warnings.
+
+## 1.3.3
+
+* Performance improvement in `Context.relative` - don't call `current` if `from`
+  is not relative.
+
+## 1.3.2
+
+* Fix some analyzer hints.
+
+## 1.3.1
+
+* Add a number of performance improvements.
+
+## 1.3.0
+
+* Expose a top-level `context` field that provides access to a `Context` object
+  for the current system.
+
+## 1.2.3
+
+* Don't cache path Context based on cwd, as cwd involves a system-call to
+  compute.
+
+## 1.2.2
+
+* Remove the documentation link from the pubspec so this is linked to
+  pub.dartlang.org by default.
+
+# 1.2.1
+
+* Many members on `Style` that provided access to patterns and functions used
+  internally for parsing paths have been deprecated.
+
+* Manually parse paths (rather than using RegExps to do so) for better
+  performance.
+
+# 1.2.0
+
+* Added `path.prettyUri`, which produces a human-readable representation of a
+  URI.
+
+# 1.1.0
+
+* `path.fromUri` now accepts strings as well as `Uri` objects.