docs: Gopkg.toml.md version

docs/Gopkg.toml.md

@@ -71,6 +71,17 @@ An `override` has the same structure as a `constraint` declaration, but supersed
   system2-data = "value that is used by another system"
 ```
 
+## `version`
+
+`version` is a property of `constraint`s and `override`s. It is used to specify
+version constraint of a specific dependency.
+
+Internally, dep uses [Masterminds/semver](https://github.com/Masterminds/semver)
+to work with semver versioning.
+
+[Why is dep ignoreing a version constraint in the manifest?](https://github.com/golang/dep/blob/master/FAQ.md#why-is-dep-ignoring-a-version-constraint-in-the-manifest)
+
+
 # Example
 
 Here's an example of a sample Gopkg.toml with most of the elements
@@ -102,4 +113,4 @@ codename = "foo"
 
   [metadata]
   propertyX = "valueX"
-```
+```