Document driver options.

docs/options.rst

@@ -0,0 +1,22 @@
+Options
+=======
+
+GDAL's format drivers have many [configuration
+options](https://trac.osgeo.org/gdal/wiki/ConfigOptions) The way to set options
+for rasterio is via ``rasterio.drivers()``. Options set on entering are deleted
+on exit.
+
+.. code-block:: python
+
+    import rasterio
+
+    with rasterio.drivers(GDAL_TIFF_INTERNAL_MASK=True):
+        # GeoTIFFs written here will have internal masks, not the
+        # .msk sidecars.
+        ...
+
+    # Option is gone and the default (False) returns.
+
+Use native Python forms (``True`` and ``False``) for boolean options. Rasterio
+will convert them GDAL's internal forms.
+

rasterio/_drivers.pyx

@@ -48,7 +48,7 @@ def driver_count():
 cdef class GDALEnv(object):
 
     cdef object is_chef
-    cdef object options
+    cdef public object options
 
     def __init__(self, is_chef=True, **options):
         self.is_chef = is_chef

rasterio/five.py

@@ -4,6 +4,8 @@ import sys
 if sys.version_info[0] >= 3:
     string_types = str,
     text_type = str
+    integer_types = int,
 else:
     string_types = basestring,
     text_type = unicode
+    integer_types = int, long