Move installer to its own repo.

https://github.com/denoland/deno_install

1. This allows the installer to use a more aggressive CI build matrix
   with different version of python.

2. Running the installer during tools/test.py artificially inflates our
   download stats.

3. Running the installer during tools/test.py makes the test script
   dependent on having an internet connection.

4. Running the installer during tools/test.py introduces a race
   condition during release - where it tries and fails to download the
   latest release in build process that should be uploading that release.

README.md

@@ -53,7 +53,7 @@
 ## Install
 
 ```
-curl -sSf https://raw.githubusercontent.com/denoland/deno/master/tools/install.py | python
+curl -sSf https://raw.githubusercontent.com/denoland/deno_install/master/install.py | python
 ```
 
 

tools/test.py

@@ -4,7 +4,6 @@
 import os
 import sys
 from check_output_test import check_output_test
-import install_test
 from util import executable_suffix, run, build_path
 from unit_tests import unit_tests
 from util_test import util_test
@@ -52,8 +51,6 @@ def main(argv):
     check_exists(deno_ns_exe)
     check_output_test(deno_ns_exe)
 
-    install_test.main()
-
 
 if __name__ == '__main__':
     sys.exit(main(sys.argv))