Ref #1, #14 - Renmaed "input" back to "Input"

- Decided to go with a standard of TitleCase for namespaces, along with source
  files. This seems to be the standard for WebKit, and that seems like a sane
  place to start.
- Renamed "input" namespace to "Input"
- Renamed axis and button names to AXIS_* and BTN_*
- Also cleaned up more uses of the std namespace, replacing it with a call to
  `using namespace std;`
- Added the `using namespace Input` to several places