Declarative application specifications for Fission (#422)

This change enables users to have declarative specifications for Fission resources. Users can specify their "app" in a set of spec files, and use a new fission CLI command to "apply" these specs to a running cluster.

The new "spec" CLI also includes archiving of local source files, and a file watcher that re-builds archives and uploads them on file changes, and a package build watcher that waits for package builds on the CLI. 

A "--spec" option is also added to "function create", and will be added to other resources in future changes.  This option causes a YAML to be outputted to the specs directory instead of the resource being created on the cluster.

The CLI "fission spec --help" outputs usage information.

examples/spec-example/hello/build.sh

@@ -0,0 +1,9 @@
+#!/bin/sh
+
+set -e
+
+# check syntax
+python -m compileall -l ${SRC_PKG}
+
+# install deps
+pip install -r ${SRC_PKG}/requirements.txt -t ${SRC_PKG} && cp -r ${SRC_PKG} ${DEPLOY_PKG}

examples/spec-example/hello/hello.py

@@ -0,0 +1,4 @@
+import yaml
+
+def main():
+    return "hello, world!!\n"

examples/spec-example/hello/requirements.txt

@@ -0,0 +1 @@
+pyyaml