getting started: hide the initial build under ./build

make build awesomer and more generic, convert to python

rename ./configure to ./download-dependencies, since it wasn't configuring
anything

.travis.yml

@@ -4,14 +4,14 @@ sudo: required
 
 install: |
   cd "$TRAVIS_BUILD_DIR"
-  bash -x ./configure --travis
+  bash -x ./download-dependencies --travis
 
 script: |
   cd "$TRAVIS_BUILD_DIR"
   # --nproc: I'm unable to install nproc on Travis.
   # TODO why? Is part of coreutils in Ubuntu 16.04:
   # http://manpages.ubuntu.com/manpages/trusty/man1/nproc.1.html
-  # which ./configure is installing.
+  # which ./download-dependencies is installing.
   #
   # awk: without it, too much stdout (4Mb max)
   # If we ignore stdout: Travis kills job because it spent