fix(travis): install virtualenv automatically

The only dependency we really have is python, and wget.
Pip is not needed !

.gitignore

@@ -1,5 +1,6 @@
 .timestamp
 .pyenv
+.virtualenv
 gen/
 *.go
 *.pyc

Makefile

@@ -1,9 +1,7 @@
 .PHONY:  json-to-xml clean help api-deps regen-apis license
 .SUFFIXES:
 
-include Makefile.helpers
-
-VENV := virtualenv
+VENV = .virtualenv/virtualenv.py
 VENV_DIR := .pyenv
 PYTHON := $(VENV_DIR)/bin/python
 PIP := $(VENV_DIR)/bin/pip
@@ -44,8 +42,13 @@ help:
 	$(info update-json  -   rediscover API schema json files and update api-list.yaml with latest versions)
 	$(info api-deps     -   generate a file to tell make what API file dependencies will be)
 
-$(PYTHON):
-	virtualenv $(VENV_DIR)
+$(VENV):
+	wget -nv https://pypi.python.org/packages/source/v/virtualenv/virtualenv-12.0.7.tar.gz -O virtualenv-12.0.7.tar.gz
+	tar -xzf virtualenv-12.0.7.tar.gz && mv virtualenv-12.0.7 ./.virtualenv && rm -f virtualenv-12.0.7.tar.gz
+	chmod +x $@
+
+$(PYTHON): $(VENV)
+	$(VENV) $(VENV_DIR)
 	$(PIP) install mako pyyaml
 
 $(MAKO_RENDER): $(PYTHON)

Makefile.helpers

@@ -1,35 +0,0 @@
-OS := $(shell uname)
-ifeq ($(OS), "")
-    OS = Windows
-endif
-
-ARCH :=
-
-# based on http://stackoverflow.com/questions/714100/os-detecting-makefile
-ifeq ($(OS),Windows)
-    ARCH = WIN32
-    ifeq ($(PROCESSOR_ARCHITECTURE),AMD64)
-        ARCH = AMD64
-    endif
-    ifeq ($(PROCESSOR_ARCHITECTURE),x86)
-        ARCH = IA32
-    endif
-else
-    UNAME_S := $(shell uname -s)
-    ifeq ($(UNAME_S),Linux)
-        OS = LINUX
-    endif
-    ifeq ($(UNAME_S),Darwin)
-        OS = OSX
-    endif
-    UNAME_M := $(shell uname -m)
-    ifeq ($(UNAME_M),x86_64)
-        ARCH = AMD64
-    endif
-    ifneq ($(filter %86,$(UNAME_M)),)
-        ARCH = IA32
-    endif
-    ifneq ($(filter arm%,$(UNAME_M)),)
-        ARCH = ARM
-    endif
-endif