Added Python 3.5 compatibility

Fixed

• Python 3.5 keyring bug fixed by @p1r473

Consistency added to initial configuration process

Added

• curate_input() function that curates user input to make sure only the expected values are entered

Changed

• made user input prompts consistent (y/n instead of y/n in some cases and yes/no in others)
• Updated README.md to include instructions for update to new version

Support for IFTTT added

New features:

• IFTTT support through Webhooks added by @ThatWeirdAndrew

Changes:

• PushBullet key is now stored using keyring