Merge pull request #188 from geertweening/fix/amount_precision

[FIX] amount precision bugs
[DOC] update release notes
[TASK] bump version to 0.9.0-rc5
[TASK] move gulp-bump to devDependencies
[FIX] confusion between precision and min_precision

`precision` expresses precision within the provided value and won't expand it if the max expression of the value is smaller
`min_precision` will expand the value if the max expression of the value is smaller