gradle.js fix versionRegex to handle prerelease

[atimonin]

Updater lib/updaters/types/gradle.js has too narrow regex for version: /^version\s+=\s+['"]([\d.]+)['"]/m, it handles only version like x.y.z while prerelease looks like x.y.z-pre.a (where x,y,z,a are numbers).
Change to /^version\s*=\s*['"]([\d.]+.*)['"]/m

[TimothyJones]

Awesome, thanks for this! Would you be able to add a test too, to stop this recurring if we ever move away from the regex?

[atimonin]

Awesome, thanks for this! Would you be able to add a test too, to stop this recurring if we ever move away from the regex?

Sorry for a long delay...
Unfortunately I'm not familiar with JS enough to write tests.
May you please merge it without tests?