Bumped up version to '0.1.3-dev'

Fixed pylint findings.

Use package_data instead of data_files arg when calling distutils.core.setup() so that the JARs will end up inside the package;
Move externals dir inside the liquipy package;
Replace single quotes with double-quotes in executor.py per Numenta coding guidelines.
Use os.path.join to create outputXmlChangeLogFilePath.
Invoke path join and split as os.path.join and os.path.split for code readability (join and split are too generic by themselves)
Fixed unwanted re-execution of previously-executed ChangeSets by using logicalFilePath attribute in databaseChangeLog. This fixes issue #13.
Added a strong WARNING comment in changeset.py about the need to persist the generated databaseChangeLog/changeSet content in order to avoid re-execution of previously-executed changesets.
Changed single-quotes to double-quotes in changeset.py per Numenta coding guidelines.
Use p.communicate() BEFORE p.wait() to avoid deadlock in case the process spits out more STDERR/STDOUT data than there is room for in the pipe's buffer (which is not that large)
Converted single quotes to double quotes in db.py per Numente coding guidelines.
Instead of the unwelcome creation of the output XML file in /tmp, use the tempfile module to create a temp file safely and then delete it when the operation completes successfully.
Fixed blank lines between class methodsin xmlwriter_test.py
Added shebang and unittest.main() execution to unit tests and made them executable (chmod +x)
Fixed unit test testYamlAbsoluteFileInclude
Fixed unit test testYamlRelativeLocalFileInclude
Fixed unit test testIncludeWithMissingDirectoryRaisesException
pylint cleanup of liquibasedb_test.py
pylint cleanup of sample_test.py
Fixed unit test xmlwriter_test.py
pylint cleanup
Fixed contamintaion of source tree with liquipy_changelog.xml file in sample_test.py
Merge pull request #12 from vitaly-krugl/work

JARs are now properly installed into the liquipy package installation directory. Bumped up version to '0.1.3-dev'. pylint cleanup. Fixes #13 and many other fixes