build: require gcc >= 5.3 and switch to C++14

Change-Id: Iba0a1fc8e4a0a0d5ec4150d4dca96792a73237e3
Refs: #3076, #4462
diff --git a/.jenkins.d/README.md b/.jenkins.d/README.md
index b1bd93a..39fa40b 100644
--- a/.jenkins.d/README.md
+++ b/.jenkins.d/README.md
@@ -13,13 +13,13 @@
 
   * `[OS_TYPE]`: `Linux`
   * `[DISTRO_TYPE]`: `Ubuntu`
-  * `[DISTRO_VERSION]`: `Ubuntu-14.04`, `Ubuntu-16.04`
+  * `[DISTRO_VERSION]`: `Ubuntu-16.04`, `Ubuntu-18.04`
 
   Possible values for OS X / macOS:
 
   * `[OS_TYPE]`: `OSX`
   * `[DISTRO_TYPE]`: `OSX` (can be absent)
-  * `[DISTRO_VERSION]`: `OSX-10.10`, `OSX-10.11`, `OSX-10.12`
+  * `[DISTRO_VERSION]`: `OSX-10.11`, `OSX-10.12`, `OSX-10.13`
 
 - `JOB_NAME`: optional variable to define type of the job.  Depending on the defined job type,
   the build scripts can perform different tasks.
@@ -29,3 +29,8 @@
   * empty: default build process
   * `code-coverage` (Linux OS is assumed): debug build with tests and code coverage analysis
   * `limited-build`: only a single debug build with tests
+
+- `CACHE_DIR`: the variable defines a path to folder containing cached files from previous builds,
+  e.g., a compiled version of ndn-cxx library.  If not set, `/tmp` is used.
+
+- `WAF_JOBS`: number of parallel build jobs used by waf, defaults to 1.