Remove superfluous check.

Remove a superfluous check for nValueIn > nValueOut in checking
transacitons.  The same is done right in the next line where it is
verified that transaction fees are non-negative.
Merge pull request #57 from domob1812/superfluous-fee-check

Remove superfluous check.
Merge branch 'rawtx-nameupdate' of github.com:domob1812/namecoin into rawtx-nameupdate