finance/py-bt: Add missing cython dependency

One dependency port was providing cython as a run-time dependency by mistake,
until this was recently fixed and exposed this build failure.

Reported by:	fallout

finance/py-bt/Makefile

@@ -13,13 +13,13 @@ WWW=		http://pmorissette.github.io/bt/
 LICENSE=	MIT
 LICENSE_FILE=	${WRKSRC}/LICENSE
 
-PY_DEPENDS=	${PYTHON_PKGNAMEPREFIX}ffn>=0.3.5:finance/py-ffn@${PY_FLAVOR} \
+PY_DEPENDS=	${PYTHON_PKGNAMEPREFIX}ffn>=1.0.0:finance/py-ffn@${PY_FLAVOR} \
 		${PYTHON_PKGNAMEPREFIX}pyprind>=2.11:misc/py-pyprind@${PY_FLAVOR}
 BUILD_DEPENDS=	${PY_DEPENDS}
 RUN_DEPENDS=	${PY_DEPENDS}
 
 USES=		python
-USE_PYTHON=	distutils autoplist pytest # tests require nose which is currently broken
+USE_PYTHON=	distutils cython autoplist pytest # tests require nose which is currently broken
 
 USE_GITHUB=	yes
 GH_ACCOUNT=	pmorissette