Bumps allocated memory from 3072 to 3584

We have more memory available, so might as well use it.
Also lowers vm.swappiness from 10 to 1.

README.md

@@ -58,7 +58,9 @@ Building Zcash
 
 The output from `gbuild` is informative. There are some common warnings which can be ignored, e.g. if you get an intermittent privileges error related to LXC then just execute the script again. The most important thing is that one reaches the step which says `Running build script (log in var/build.log)`. If not, then something else is wrong and you should let us know.
 
-Take a look at the variables near the top of `~/gitian-build.sh` and get familiar with its functioning, as it can handle most tasks. It's also a good idea to `git pull` on this repository in order to obtain updates (while using `git stash` to save one's customizations to `gitian.yml`) and re-run the entire VM provisioning for each release to ensure current and consistent state for your builder.
+Take a look at the variables near the top of `~/gitian-build.sh` and get familiar with its functioning, as it can handle most tasks. I
+
+It's also a good idea to regularly `git pull` on this repository to obtain updates (while using `git stash` to save one's customizations to `gitian.yml`) and re-run the entire VM provisioning for each release, to ensure current and consistent state for your builder.
 
 Generating and uploading signatures
 -----------------------------------

roles/common/defaults/main.yml

@@ -1,6 +1,6 @@
 ---
 zcash_swapfile_size: 1G
-zcash_vm_swappiness: 10
+zcash_vm_swappiness: 1
 zcash_common_packages:
   - apt-show-versions
   - apt-transport-https

roles/gitian/templates/gitian-build.sh

@@ -16,7 +16,7 @@ VERSION={{ zcash_version }}
 commit=false
 url={{ zcash_git_repo_url }}
 proc=2
-mem=3072
+mem=3584
 lxc=true
 scriptName=$(basename -- "$0")
 signProg="gpg2 --detach-sign"
@@ -40,7 +40,7 @@ Options:
 -s|--sign	Make signed binaries
 -B|--buildsign	Build both signed and unsigned binaries
 -j		Number of processes to use. Default 2
--m		Memory to allocate in MiB. Default 3072
+-m		Memory to allocate in MiB. Default 3584
 --detach-sign   Create the assert file for detached signing. Will not commit anything.
 --no-commit     Do not commit anything to git
 -h|--help	Print this help message