Inconsistent "DirectMedia" capitalization in repo metadata and README

[Splendide-Imaginarius]

The repository metadata on GitHub says:

Simple Directmedia Layer

Meanwhile the README says:

Simple DirectMedia Layer (SDL for short) is a cross-platform library designed to make it easy to write multi-media software, such as games and emulators.

The capitalization of the "M" in "DirectMedia" is inconsistent between the two.

[icculus]

Should be lowercase m, imho.

[slouken]

Originally was uppercase, but I don't have a strong preference at this point.

[slouken]

The copyright on every file uses "Simple DirectMedia Layer", so I fixed the repository metadata.

Thanks!