Add test utils and get_doc helper function

Create Doc object from given vocab, words and annotations to allow
tests not to depend on loading the models.

spacy/tests/util.py

@@ -0,0 +1,21 @@
+# coding: utf-8
+from __future__ import unicode_literals
+
+from ..tokens import Doc
+from ..attrs import ORTH, POS, HEAD, DEP
+
+
+def get_doc(vocab, words, tags=None, heads=None, deps=None):
+    """Create Doc object from given vocab, words and annotations."""
+    tags = tags or [''] * len(words)
+    heads = heads or [0] * len(words)
+    deps = deps or [''] * len(words)
+
+    doc = Doc(vocab, words=words)
+    attrs = doc.to_array([POS, HEAD, DEP])
+    for i, (tag, head, dep) in enumerate(zip(tags, heads, deps)):
+        attrs[i, 0] = doc.vocab.strings[tag]
+        attrs[i, 1] = head
+        attrs[i, 2] = doc.vocab.strings[dep]
+    doc.from_array([POS, HEAD, DEP], attrs)
+    return doc