Suggestion: remove tests from the distribution
Would it make sense to remove `tests` folder from the pandas distribution? It takes roughly 33% of the whole package weight. 

It is especially important when using pandas inside the AWS Lambdas, where the deployment package size is limited to 50 MB zipped and 5 MB might really make a difference.

```
# Uncompressed
du -h -s pandas*
 46.5M	pandas
 30.9M	pandas_no_tests

# Compressed
du -h -s pandas*
 14.7M	pandas.zip
 10.1M	pandas_no_tests.zip
```