use absolute imports for Python 3 compatibility

pysstv/__main__.py

@@ -4,8 +4,7 @@ from __future__ import print_function
 from PIL import Image
 from argparse import ArgumentParser
 from sys import stderr
-import color
-import grayscale
+from pysstv import color, grayscale
 
 SSTV_MODULES = [color, grayscale]
 

pysstv/color.py

@@ -1,8 +1,8 @@
 #!/usr/bin/env python
 
 from __future__ import division
-from sstv import byte_to_freq, FREQ_BLACK, FREQ_WHITE, FREQ_VIS_START
-from grayscale import GrayscaleSSTV
+from pysstv.sstv import byte_to_freq, FREQ_BLACK, FREQ_WHITE, FREQ_VIS_START
+from pysstv.grayscale import GrayscaleSSTV
 from itertools import chain
 
 

pysstv/grayscale.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python
 
 from __future__ import division
-from sstv import SSTV, byte_to_freq
+from pysstv.sstv import SSTV, byte_to_freq
 
 
 class GrayscaleSSTV(SSTV):

pysstv/tests/test_color.py

@@ -5,7 +5,7 @@ import pickle
 from PIL import Image
 
 from pysstv import color
-from common import get_asset_filename
+from pysstv.tests.common import get_asset_filename
 
 
 class TestMartinM1(unittest.TestCase):