Refactored for multi-OS usage.

Refactored with creation of OsSpoofer abstract class for MAC spoofing.
Added Linux support for MAC spoofing.  Minor bug fix on usage for -h.
Merged from upstream (original) - lastest greatest code
Ignore swap files from VIM
Updated comment on Linux and bumped ver.
Added support for multiple OS

1) Created OsSpoofer abstract class
2) Implemented Windows spoofing via registry
3) Merged Mac spoofing logic into MacSpoofer
4) Added specific return codes for spoof-mac
5) Updated readme and code comments
Removed brackets & clean-up linux platform check.

Be more pythonic.
Removed UnsupportedPlatformException

no need for custom exception - use built-in instead.
Singleton removed clean up comments
Removed shell=True

Potential security hazard and not required.
Added support for Linux
Merge pull request #14 from cjbarker/master

Added support for Windows and Linux.