Give option on how git tracks submodules.

Allows user to decide if git submodule should track branches/tags or track commit hashes defined in the superproject.

Add track_branches parameter to the git module.

Defaults to track branches behavior.
Chnge option name to track_submodule_branches.

Update documentation to reflect what the actual effect of the option.
Fixed really annoying omission in the example without the task would complete without errors or warnings but delete all egress rules
Update syntax for cloudformation example
fields in /proc/net/tcp* are not always delimited by single space
ec2_snapshot: document wait, wait_timeout params

Document the wait and wait_timeout params for ec2_snapshot.

This is important because snapshots can take a long time to complete,
and the module defaults to wait=yes.
Merge pull request #217 from jnsaff/fix-ec_group-documentation

Added cidr_ip to ec_group rules_egress example in documentation.
Merge pull request #219 from adamchainz/devel

Update syntax for cloudformation example
Merge pull request #222 from ranjanashish/devel

fields in /proc/net/tcp* are not always delimited by single space
Merge pull request #230 from lorin/ec2_snapshot_wait

ec2_snapshot: document wait, wait_timeout params
Merge pull request #55 from bibliotechy/add-track-submodule-branches-parameter

Add track submodule branches parameter
Update desctiprion, parameter name, and default value as discussed in #55
Fix git module handling of the recursive flag

Fixes: #169
LinuxService: check properly if systemd is running

Use a pure Python reimplementation of the [sd_booted(3)][1] function
from [systemd v210][2].

[1]: http://www.freedesktop.org/software/systemd/man/sd_booted.html
[2]: http://cgit.freedesktop.org/systemd/systemd-stable/tree/src/libsystemd/sd-daemon/sd-daemon.c?id=v210#n465
Transform comment into docstring
LinuxService: use the same logic as systemd for appending .service to an unit

There's no need for complex rules to determine if `.service` should be
appended to a unit's name, just do like systemd does.  For more details
see commit [696c245a23d55e4249651573eb9c61b68e61580c][1] and
[`unit_name_mangle`][2] from systemd.

[1]: http://cgit.freedesktop.org/systemd/systemd/commit/?id=696c245a23d55e4249651573eb9c61b68e61580c
[2]: http://cgit.freedesktop.org/systemd/systemd/tree/src/shared/unit-name.c?id=696c245a23d55e4249651573eb9c61b68e61580c#n501
LinuxService: check properly if systemd manages the unit

There's no need to list and look at all the unit files, just check the
[load state][1] of the current unit by running `systemctl -p LoadUnit show`.

This also covers cases like when an unit is masked (which means that
systemd can't start or enable it).

[1]: http://cgit.freedesktop.org/systemd/systemd-stable/tree/src/shared/unit-name.c?h=v208-stable#n52
LinuxService.get_service_tools: check for systemd first

Check for systemd first then for legacy init systems. This simplifies
the code.
LinuxService: d.get(k, None) -> d.get(k)

From the documentation:
> D.get(k[,d]) -> D[k] if k in D, else d.  d defaults to None.

So there's no need for the `None` parameter.