Copied comments for matrix.
Copied comments for path
Copied more documentation from Cairo.
Documented members of Matrix.
Added documentation for Format.
Added documentation for SurfaceType and DeviceType.
Added documentation for Content.
Added more documentation for Surface and Device.
Completed copying documentation for surface
Added documentation for hint_metrics
Copied documentation from Cairo for hint_style
Copied documentation from Cairo for subpixel_order
Copied documentation from Cairo for font weight
Copied documentation from Cairo for font slant
Copied documentation from Cairo for font type
Copied documentation from Cairo for font cluster flags
Copied documentation from Cairo for font
Copied Cairo documentation for region overlap
Copied Cairo documentation for region
Splitted pattern.rs into several files.