add basic camera code.

not quite sure yet why camera = focus works.

js/pixl/public/trixl.html

		program.color = gl.getUniformLocation(program, 'color');
		gl.uniform4f(program.color, -1, -1, -1, -1);
		trixl.pos = {x: 0, y: 0, z: 0, a: 0};
		var angle = {x: 0, y: 0, z: 0};
		var offset = {x: 0, y: 0, z: 0};
		program.transform = gl.getUniformLocation(program, 'transform');
		trixl.redraw = function() {
			var camera = mat4.multiplyMany(
				matrix.translate(trixl.pos.x, trixl.pos.y, trixl.pos.z),
				matrix.rotateY(trixl.pos.a)
			);
			var camera_pos = [camera[12], camera[13], camera[14]];
			var up = [0, 1, 0];
			camera = mat4.lookAt([], camera_pos, [0, 0, 0], up);
			var view = mat4.invert([], camera);
			var aspect = trixl.window.w / trixl.window.h;
			var transform = function(pos) {
				return mat4.multiplyMany(
					//matrix.rotateY(angle.y / 10),
					matrix.rotateX(angle.x / 10),
					matrix.translate(pos[0] + offset.x, pos[1] + offset.y, pos[2] + offset.z),
					view,
					matrix.persective(Math.PI / 3, aspect)
				);
			}