Fix bug with TypeError: 'str' does not support the buffer interface

Bug occurred when behind a corporate proxy,
confirmed on Windows XP, Windows 7, OS X 1.8.2

Credit goes to @holjan for the code
Exclude the package User from package commands.
Initial support for installing a package as a .sublime-package file
Fixed detection of already installed packages
Fixed duplicate code that was trying to remove the same package file twice
Added check to handle situations where there is no package folder to remove
Changed the way that package_io looks for files, first checking the package folder, then the package file
Merged pull request #331 - exclude the "User" package from the list and remove operations
Removed the strict parameter from HTTP classes since Python 3.2 deprecated it, and PC never uses it
Merged pull request #324 - fixed HTTPS proxy code to write and read bytes for Python 3