[SPARK-6219] [Build] Check that Python code compiles

This PR expands the Python lint checks so that they check for obvious compilation errors in our Python code.

For example:

```
$ ./dev/lint-python
Python lint checks failed.
Compiling ./ec2/spark_ec2.py ...
  File "./ec2/spark_ec2.py", line 618
    return (master_nodes,, slave_nodes)
                         ^
SyntaxError: invalid syntax

./ec2/spark_ec2.py:618:25: E231 missing whitespace after ','
./ec2/spark_ec2.py:1117:101: E501 line too long (102 > 100 characters)
```

This PR also bumps up the version of `pep8`. It ignores new types of checks introduced by that version bump while fixing problems missed by the older version of `pep8` we were using.

Author: Nicholas Chammas <nicholas.chammas@gmail.com>

Closes #4941 from nchammas/compile-spark-ec2 and squashes the following commits:

75e31d8 [Nicholas Chammas] upgrade pep8 + check compile
b33651c [Nicholas Chammas] PEP8 line length