Implement Python 2.7 compatibility

- Add 'optionparser' backport as a dependency when installing with Python 2
- Use Python 2.7.6 as default version when building with Python 2
- Include pylauncher in MSI when building with Python 2
Update the file with Python public keys.

Generated the keys file using these commands:

gpg --recv-keys 6A45C816 36580288 7D9DC8D2 18ADD4FF A4135B38 A74B06BF EA5BBD71 ED9D77D5 E6DF025C 6F5E1540 F73C700D
gpg --armor --export 6A45C816 36580288 7D9DC8D2 18ADD4FF A4135B38 A74B06BF EA5BBD71 ED9D77D5 E6DF025C 6F5E1540 F73C700D > python-pubkeys.txt

The list of key IDs was copied from this page:
https://www.python.org/download
Improve handling of ZIP files in Python 2
Stylistic fixes
Fix console example
Fix typo in copymodules
Remove explicit Python versions from example configurations
Reinstate explicit Python version for PyQt example
Merge pull request #9 from jbaiter/py27

Implement Python 2.7 compatibility
Simplify error checking
Refactor NSISWriter to make template filling easier
Separate files and directories for .nsi templating
Add release notes
Add support for multiple shortcuts

Closes gh-6
Document defining multiple shortcuts
Use non-importable name for entry point launcher scripts.

Avoids them conflicting with packages when we try to e.g. 'import
IPython'.
Add script to build all examples
Guard shortcut script with 'if __name__ == __main__' to avoid side-effects when using multiprocessing