Skills increase don't handle wrap around.

[jlnunez89]

Problem

When a skill is increased, a value by which to increase the current count is supplied.
That value is only accounted for up until the next skill level and the count is reset to the beginning of that 'next level'.
i.e. when a skill advances, the percent is always reset to zero when in reality, it should be left at where the increase lands it.

Solution

The added value should 'wrap around' such that multiple skill level advances are possible by increasing by a big enough value.
This should be addressed in Fibula.Creatures/Skill.cs and Fibula.Creatures/MonsterSkill.cs respectively.

[jlnunez89]

leaving up for grabs since it's a good first issue.