Don't arbitrarily limit set_mark to certain chains

set_mark is not only allowed in PREROUTING or OUTPUT chain,
but also in custom chains, which are called from these.
FM-2022 Add SLES 12 to metadata
README cosmetics
Merge pull request #439 from cmurphy/master

Update .travis.yml, Gemfile, Rakefile, and CONTRIBUTING.md
MODULES-1572 - Fix logic broken from MODULES-1309

Accidentally changed some behavior and broke things with the fix for
MODULES-1309
Merge pull request #441 from mhaskel/MODULES-1572

MODULES-1572 - Fix logic broken from MODULES-1309
Merge pull request #437 from alexjurkiewicz/master

README cosmetics
Merge pull request #434 from cyberious/master

FM-2022 Add SLES 12 to metadata
MODULES-556: tcp_flags support for ip6tables

tcp_flags was listed as a supported feature for the ip6tables provider,
but it wasn't actually implemented
Merge pull request #442 from mhaskel/MODULES-556

MODULES-556: tcp_flags support for ip6tables
Merge pull request #427 from stesie/fix-set_mark-limit

Don't arbitrarily limit set_mark to certain chains
1.3.0 prep
Merge pull request #443 from mhaskel/1.3.0-prep

1.3.0 prep
Add netmap feature and acceptance tests
Merge pull request #444 from mhaskel/merge_1.3.x_into_master

Merge 1.3.x into master
Updates to format to fit style guide.
Merge pull request #445 from laurenrother/master

Updates to format to fit style guide.
Merge pull request #421 from nemski/bug/master/add_netmap

(MODULES-464) Add netmap feature
Fix netmap acceptance tests

This commit:
  - Updates the netmap acceptance tests to have the correct identifying
    comment
  - Resets iptables inbetween the two tests since the rules can't be
    changed
  - Updates a regex in the iptables provider to check for spaces before
    and after a flag so that "--to" isn't confused with "--to-port"
Merge pull request #448 from cmurphy/fix_tests

Fix netmap acceptance tests