Incremented minor version,

in order to indicate that the addition of a function to assign a
particular value to a version part is a new feature. This resolves #19
(https://github.com/ploeh/ZeroToNine/issues/19).
Accepted only properly formatted version strings

for assignment operation.
Refactored IntegerGreaterThanOrEqualToZero

partial active pattern in order to simplify it a bit.
Ensured that the assign operation can handle

partial version strings.
Incremented patch version,

in order to indicate that checking for a properly parse version string
when assigning a version, constitutes a fix, in the sense that it's better
input validation.
Removed some redundant paratheses.
Made 'assign version component' a titled paragraph.
Added Unquote NuGet package to ZeroToNine tests.
Converted all ZeroToNine unit tests to unquote

assertions.
Added Unquote NuGet package to Zero29 unit tests.
Converted all assertions in Zero29 unit tests

to Unquote.