Bug: Import-Module fails for prerelease versions (semver suffix passed as RequiredVersion)

[HeyItsGilbert]

Problem

When a prerelease version like 1.2.3-alpha is specified, PSDepend passes the full string including
the prerelease suffix to Import-Module -RequiredVersion, which only accepts System.Version format.

Related

Tracked in #132. Fix is to strip the prerelease suffix before calling Import-Module.
PR #140 addresses this — review and merge.

Impact

Affects any user depending on prerelease module versions.