Fix #183 (short term fix)

This is a temporary fix for #183, so that things can
build cleanly until the issue is fixed properly.

If RIMESTATS_CONF_ENABLED is 0, rimestats.foo will always
read as 0, since RIMESTATS_ADD(foo) doesn't do anything
Provide a macro to read rimestats when enabled
Rename RIMESTATS_CONF_ON to RIMESTATS_CONF_ENABLED
Replace reads of rimestats with RIMESTATS_GET(x)
Travis: Print out logs so that debugging travis is possible.
Travis: correct the name for the ipv6-apps test (travis.yml had the correct name
--- this is why the test was failing)
Travis: fix the download location for the arm/mc1322x toolchain
Travis: Run java with -Xshared:on. The previous jvm had shared on by default and cooja
requires this.
Travis: The test criteria for this test was too strict --- one or two
packets get lost. Change the test to ensure that data comes back from
every node and we get at least 75 non-duplicate reports.
Travis: disable flaky or failing tests

* disable hello-world of cooja motes b/c it is flaky
* mark 04-sky-shell-download.csc test as failing. Not sure what
the problem is.
Travis: sky-ipv6-udp test needs more time to complete
Merge pull request #230 from malvira/pr-travis-fixes

Travis fixes
Remove everything that depended on the now gone twitter APP.
Merge pull request #231 from malvira/pr-remove-twitter

Remove everything that depended on the now gone twitter APP.
change default UIP_CONF_IPV6 back to 0. This is not a complete fix:
see #227 for details. Will merge as it fixes build errors so Travis
can be useful agian.
Merge pull request #232 from malvira/pr-uip6-switch-temp-fix

change default UIP_CONF_IPV6 back to 0. This is not a complete fix:
Merge pull request #228 from g-oikonomou/bug-fixes/uip-conf-ipv6

Fix 8051 port builds to play nicely with #173
Travis: disable the netperf test because it is flaky
Merge pull request #233 from malvira/pr-disable-netperf

Travis: disable the netperf test because it is flaky
Merge pull request #184 from g-oikonomou/bug-fixes/rimestats

Rimestats Fix (#183)