Update pyls hover to specify language of signature.

LSP supports `MarkedString[]` to specify render engine. We can definitely
say that function signature should be rendered as python. For the docstring,
as we have no good way of parsing it to guess the engine, we can pass it
as markdown.

Author: mpanarin

pyls/plugins/hover.py

@@ -13,6 +13,15 @@ def pyls_hover(document, position):
     # Find an exact match for a completion
     for d in definitions:
         if d.name == word:
-            return {'contents': _utils.format_docstring(d.docstring()) or ''}
+            doc = _utils.format_docstring(d.docstring()).split("\n", 1)
+            if not doc:
+                return {'contents': ''}
+            contents = [{
+                "language": "python",
+                "value": doc[0],
+            }]
+            if len(doc) > 1:
+                contents.append(doc[1])
+            return {'contents': contents}
 
     return {'contents': ''}