Updated travis build file to use nosetests so Travis build will fail when there are failing tests

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Added get_global_param_string to the DLL wrapper
Made other DLL outputs return long rather than being void

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Merge branch 'master' of https://github.com/ibell/coolprop

Conflicts:
	CoolProp/gitrevision.h

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>