Include colorama as a dependency for pip-compile.

setup.cfg

@@ -49,6 +49,13 @@ install_requires =
     treq
     pyutil
     prometheus-client
+    # Include colorama as a dependency to help pip-compile deal with multiple
+    # platforms.  In particular, tqdm depends on colorama only on Windows. By
+    # including it here, pip-compile will generate hashes (and install it) on
+    # all platforms. colorama and pywin32 are our only depdencies that are only
+    # required on some platforms; we can't include pywin32 here as it does not
+    # install cross-platform.
+    colorama
 
 [options.extras_require]
 test = coverage; fixtures; testtools; hypothesis