Vagrant: check out pyinstaller code from master branch

they just recently released 3.0 and that is in master now

Vagrantfile

@@ -204,7 +204,7 @@ def install_pyinstaller(boxname)
     . borg-env/bin/activate
     git clone https://github.com/pyinstaller/pyinstaller.git
     cd pyinstaller
-    git checkout develop
+    git checkout master
     pip install -e .
   EOF
 end
@@ -216,7 +216,7 @@ def install_pyinstaller_bootloader(boxname)
     . borg-env/bin/activate
     git clone https://github.com/pyinstaller/pyinstaller.git
     cd pyinstaller
-    git checkout python3
+    git checkout master
     # build bootloader, if it is not included
     cd bootloader
     python ./waf all