Fix regex for parsing difficulty data

[tsweet64]

I experienced an issue where parsing the .osu files failed due to the match() returning null. This seems to have been because my files had spaces separating the keys and values, like HPDrainRate: 3 instead of HPDrainRate:3 and because some values were pure integers with no decimals (I use osu!lazer, so perhaps these are differences from the stable version). This commit updates the regex to accommodate files with or without spaces, and values with or without decimal points.

[ArmandoRl1]

Yup. Preety simple fix. Please add this.