rWebUnit renamed to RWebSpec

[Zhimin]

Hi all,

rWebUnit test framwork is an extension of Watir, and the preferred
test framework supported by iTest2.

The name does not match its real use: functional testing, not unit
testing. So it is renamed to "RWebSpec", which stands for "Web
application specification in Ruby". The new RWebSpec 1.4 version is
included in PRoR v21.

After upgrading to RWebSpec, you existing test scripts shall work as
it is.

Cheers,
Zhimin