Make _spec suffix optional when running `rake spec files=...`
Make _spec suffix optional when running `rake spec files=...`

With this change, the following invocations are equivalent:

    rake spec files=integration_spec

and

    rake spec files=integration

HipByte/RubyMotion,beni55/RubyMotion,hboon/RubyMotion,hboon/RubyMotion,jjaffeux/RubyMotion,beni55/RubyMotion,katsuyoshi/RubyMotion,beni55/RubyMotion,incbee/RubyMotion,incbee/RubyMotion,katsuyoshi/RubyMotion,HipByte/RubyMotion,katsuyoshi/RubyMotion,HipByte/RubyMotion,hboon/RubyMotion,jjaffeux/RubyMotion,incbee/RubyMotion,jjaffeux/RubyMotion,incbee/RubyMotion,beni55/RubyMotion,katsuyoshi/RubyMotion,jjaffeux/RubyMotion