Break after we find a path
Use EvalSymlink to fix case issues on Windows

On Windows, if $GOPATH = "c:\gopath", the previous code would not match
that directory because it was checking for "C:\gopath\src\...".
Show configured paths on verbose
Spelling
make thiry_party directory name configurable (eg; party -c -t 3rdParty)
[cosmetic] use flag.BoolVar and flag.StringVar
use the last element of the path