Add vaex package. (#1079)

Fixes #928. Original PR is #1031 (thanks @JovanVeljanoski)

- Includes a test.

http://b/191699352

Author: rosbo

Dockerfile.tmpl

@@ -407,6 +407,7 @@ RUN pip install bleach && \
 
 RUN pip install flashtext && \
     pip install wandb && \
+    pip install vaex && \
     pip install marisa-trie && \
     pip install pyemd && \
     pip install pyupset && \

tests/test_vaex.py

@@ -0,0 +1,10 @@
+import unittest
+
+import vaex
+
+class TestVaex(unittest.TestCase):
+    def test_read_csv(self):
+        df = vaex.read_csv("/input/tests/data/train.csv")
+
+        self.assertEqual((100, 785), df.shape)
+        self.assertEqual(10, df['label'].nunique())