Implement modin.pandas.DataFrame.align

[devin-petersohn]

Describe the problem

Currently, align is not implemented for DataFrame objects.

Source code / logs

In [1]: import modin.pandas as pd
   ...: import numpy as np
   ...: 
   ...: frame_data = np.random.randint(0, 100, size=(2**12, 2**8))
   ...: df = pd.DataFrame(frame_data)
   ...: 
   ...: 
Process STDOUT and STDERR is being redirected to /tmp/raylogs/.
Waiting for redis server at 127.0.0.1:24882 to respond...
Waiting for redis server at 127.0.0.1:55764 to respond...
Starting the Plasma object store with 27.00 GB memory.
Starting local scheduler with the following resources: {'GPU': 0, 'CPU': 8}.

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View the web UI at http://localhost:8888/notebooks/ray_ui89247.ipynb?token=ca5e30c50fb8d5a3bc873a8adf2539198dbfef8b003ff195
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In [2]: df.align(df)
---------------------------------------------------------------------------
NotImplementedError                       Traceback (most recent call last)
<ipython-input-2-afa7038926eb> in <module>()
----> 1 df.align(df)

~/anaconda/lib/python3.5/site-packages/modin/pandas/dataframe.py in align(self, other, join, axis, level, copy, fill_value, method, limit, fill_axis, broadcast_axis)
   1094               broadcast_axis=None):
   1095         raise NotImplementedError(
-> 1096             "To contribute to Pandas on Ray, please visit "
   1097             "github.com/modin-project/modin.")
   1098 

NotImplementedError: To contribute to Pandas on Ray, please visit github.com/modin-project/modin.

[devin-petersohn]

Close to track #1185