Bump version to 5.0b3

5.0b1 merge fixes (apple#625)

* Fix bad merges from the other 5.0b1 feature PRs
* Bump version to 5.0b1
* Bump dependency versions to the tested versions
* Add support for Vision Feature Print in the image deep feature
  extractor
* Includes table printer fixes
* Includes some performance fixes
* Includes some Python 3 compat fixes

Bump version to 4.3.2.

Bump version number to 4.3.1

Merge branch 'master' into release_4.3

Fix C++ unit test failure, attempt apple#2 (apple#339)

The `readsome` function doesn't behave the way I expected - "available"
means "already in the buffer", not "can be read from the stream", which
means typically it reads 0 bytes on a newly initialized stream (which
breaks skip_BOM). We need to use `get`, and after each call, make sure
the stream is still in a good state (or recover if it's not).

This one passes both the C++ unity_sarray.cxxtest and Python
test_sframe.py.

Use binary mode to read README.rst (apple#282)

Then decode utf-8 explicitly. For some reason, otherwise we get:

```
+ VERSION_NUMBER=4.1.1
+ /builds/turi/turicreate-build/scripts/../deps/env/bin/python setup.py
bdist_wheel
Traceback (most recent call last):
  File "setup.py", line 127, in <module>
    long_description = f.read()
  File
"/builds/turi/turicreate-build/scripts/../deps/env/lib/python3.5/encodings/ascii.py",
line 26, in decode
    return codecs.ascii_decode(input, self.errors)[0]
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2 in position
106: ordinal not in range(128)
```

Add more documentation datasets (apple#251)

Clean up file drop

* Restore README.md (delete README.txt)
* Delete dummy.cpp and add to .gitignore (this gets created every build)
* Remove stray .gitattributes