Shouldn't allow to do rake install unless version is specified

[snitko]

When I'm developing a new gem and forget to set the initial version and then I run rake install, the gem installs into a rubygem dir under gem_name- which prevents rubygems from working correctly. I end up reinstalling ruby completely.

There should be a check not allowing to perform rake install unless the version is set.

[flajann2]

Good catch. Thanks.