MNT: Populate fsl.installer namespace with everything from the script

fsl/installer/__init__.py

+#!/usr/bin/env python
+#
+# The fsl.installer package just imports all of the useful functions from
+# the fslinstaller.py script, so that other scripts can "import fsl.installer"
+# instaed of "fsl.installer.fslinstaller"
+
+from fsl.installer.fslinstaller import *