enabling cpp-netlib to be compiled into a single library

including uri
fix duplicate target definition
Merge pull request #10 from torbjoernk/make-one-cppnetlib-lib

enabling cpp-netlib (and uri) to be compiled into a single library
Made uri.cpp compile with msvc 2012
Made scheme part optional to allow parsing of a URI reference
Fixed broken tests in uri::relativize
Implemented some trivial cases for uri::resolve
Merge branch 'master' of https://github.com/hansmaad/uri