Created Context Class

This class will handle creation and memory management for OpenGL
contexts.
Added setActive Method To Context

Sets the context to either active or inactive.
Added Context Creation

The Context class can now create itself for a specific window and GL
version.
Added Error Checking

Context::setActive() now handles errors and reports them to the user.
Added Context Checking

Contexts can be checked now as a bool to see if they're valid or not.
Changed Context::setActive()

It now takes a reference to a Window object rather than an SDL_Window
pointer.
Construct Window From Existing

Window can now take an already-created SDL_Window* and use it as its
internal window.
Make Window Non-copyable And Non-movable

Added copy/move constructors and operators to prevent these operations
on a window.
Make Context Non-copyable And Non-movable

Added copy/move constructors and operators to prevent these operations
on a context.
Added Simple Context::create()

This version takes a window and constructs the context with the
currently-set flags.
Fixed Simple Errors