Fix import error during setup.py install

Hey there,

Thanks for the AMAZING lib.

Unfortunately it currently can't be installed unless requests has previously been installed. 

- setup.py import libgreader (for version/author)
- libgreader import all its submodules
- some of these submodules import requests

This means requests is required to be installed prior to libgreader being installed. requests is listed as a dependency in setup.py, but it won't ever get automatically installed since setup.py will fail without it.

This commit simply wraps the submodule imports inside libgreader in a try/catch for importing requests - it'll fail during install, which is expected and fine, then succeed when the lib is actually used, and requests is installed.

Unfortunately this affects the current version uploaded to pypi - so anyone trying to install libgreader from there right now will receive this error, so it might be worthwhile pushing this change up as 0.7.1 or 0.8 asap.

Thanks again!