Option to expand image disk size

[jywarren]

(Noting to help document!) I ran into a problem running out of disk space in this recipe: #37

@icarito pointed me at this line which we can change to double the disk size from 1GB to 2GB:

https://github.com/publiclab/pi-builder/blob/f9481e45f189ba1e7b15c6a6c2dd364b31540547/builder/build.sh#L87

Here's the commit i used to make the change:

https://github.com/publiclab/pi-builder/pull/37/commits/bd98bbeea44471d14edd9464455b3f81294ddc95

-  wget -q -O "${BUILD_RESULT_PATH}/${RAW_IMAGE}.zip" "https://github.com/hypriot/image-builder-raw/releases/download/${RAW_IMAGE_VERSION}/${RAW_IMAGE}.zip"
+  wget -q -O "${BUILD_RESULT_PATH}/${RAW_IMAGE}.zip" "https://jenkins.laboratoriopublico.org/job/image-builder-raw/ws/${RAW_IMAGE}.zip"

Additionally, the checksum in /versions.config must be modified:

-RAW_IMAGE_VERSION="v0.2.2"
-RAW_IMAGE_CHECKSUM="2fbeb13b7b0f2308dbd0d82780b54c33003ad43d145ff08498b25fb8bbe1c2c6"
+RAW_IMAGE_VERSION="master"
+RAW_IMAGE_CHECKSUM="e32c0b9f3cdb9c60bad97a724103fc1283cdc135848e6142d588cd96fac1d6a8"