New framework: Pumbaa (#7)

* New framework: Pumbaa

Pumbaa is MicroPython on top of Simba.

The framework will generate a file called frozen.c from all .py files
found in the project src/ folder. The script file main.py is the entry
point for the user script. If main.py is missing the application will
enter the interactive Python interpreter.

All c/cpp source files (including frozen.c) will be compiled, linked
and uploaded as an ordinary c application.

http://pumbaa.readthedocs.io/en/latest/

* Added pumbaa-blink example to appveyor.

builder/frameworks/pumbaa.py

@@ -0,0 +1,60 @@
+# Copyright 2014-present PlatformIO <contact@platformio.org>
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Pumbaa
+
+Pumbaa is Python on top of Simba.
+
+The implementation is a port of MicroPython, designed for embedded
+devices with limited amount of RAM and code memory.
+
+http://pumbaa.readthedocs.org
+
+"""
+
+from os.path import join, sep
+
+from SCons.Script import DefaultEnvironment, SConscript
+
+from platformio.builder.tools import platformio as platformio_tool
+
+#
+# Backward compatibility with PlatformIO 2.0
+#
+platformio_tool.SRC_DEFAULT_FILTER = " ".join([
+    "+<*>", "-<.git%s>" % sep, "-<svn%s>" % sep,
+    "-<example%s>" % sep, "-<examples%s>" % sep,
+    "-<test%s>" % sep, "-<tests%s>" % sep
+])
+
+
+def LookupSources(env, variant_dir, src_dir, duplicate=True, src_filter=None):
+    return env.CollectBuildFiles(variant_dir, src_dir, src_filter, duplicate)
+
+
+def VariantDirWrap(env, variant_dir, src_dir, duplicate=False):
+    env.VariantDir(variant_dir, src_dir, duplicate)
+
+
+env = DefaultEnvironment()
+
+env.AddMethod(LookupSources)
+env.AddMethod(VariantDirWrap)
+
+env.Replace(
+    PLATFORMFW_DIR=env.PioPlatform().get_package_dir("framework-pumbaa")
+)
+
+SConscript(
+    [env.subst(join("$PLATFORMFW_DIR", "make", "platformio.sconscript"))])