zulip_bots: Move installation of bot deps to tools/provision.

A lot of these bot dependencies are pretty hefty and shouldn't be
installed as part of the zulip_bots package. So the installation of
these belongs in tools/provision, not in setup.py.

tools/provision

@@ -4,6 +4,7 @@ import os
 import sys
 import argparse
 import subprocess
+import glob
 
 from importlib import import_module
 
@@ -93,6 +94,17 @@ the Python version this command is executed with."""
     if py_version > (3, 1):
         install_dependencies('py3_requirements.txt')
 
+    # Install all requirements for all bots. get_bot_paths()
+    # has requirements that must be satisfied prior to calling
+    # it by setup().
+    current_dir = os.path.dirname(os.path.abspath(__file__))
+    bots_dir = os.path.join(current_dir, "..", "zulip_bots", "zulip_bots", "bots")
+    req_paths = glob.glob(bots_dir + "/*/requirements.txt")
+    for req_path in req_paths:
+        path_split = req_path.split(os.path.sep)[-5:]
+        relative_path = os.path.join(*path_split)
+        install_dependencies(relative_path)
+
     print(green + 'Success!' + end_format)
 
     activate_command = os.path.join(base_dir,