Bugfix: known_hosts file was not always deleted when the cluster was terminated.
Update documentation related to the automatically created known_hosts
file when using `elasticluster ssh` and `elasticluster sftp`
Add option `ssh_pipelining` to enable/disable ssh pipelining when running ansible. By default it's enabled.
Add fix to allow loading of a cluster created *before* the addition of option `ssh_pipelining`
Fix error when trying to remote non-existing known_hosts file
Add support for Amazon VPC clusters.
Thanks to John Morrissey (https://github.com/jwm)
Also parse ~/.elasticluster/config.d/*.conf if it exists, for more clusters.
OpenStack provider now *override* configuration options for `username`, `password` and `project_name` if a corresponding environment variable is defined.
This allow you to define fake values for, e.g. `password` and avoid putting sensible data in the config file.
Fixes issue #122 "elasticluster checks SSH key even if it's
password-protected"

If private key is protected by a password, do not check if the
fingerprint of the keypair matches, since paramiko RSAKey/DSAKey
classes only gets you the fingerprint from a pair public/private key.

(well, this I should check more carefully, but for the time being it's fine)
Ugly fix to allow overriding option `ssh_to` for a cluster which is already started
Update ansible playbooks
Squashed 'elasticluster/providers/ansible-playbooks/' changes from 15493d4..f4141ea

f4141ea cosmetic changes
34137b7 Remove `blacs-openmpi` package which is not available on CentOS 6 (apparently)
37770c9 Add support for SLURM on CentOS 6 (Needs to download and compile slurm)
98af8db update `nfsexport` module: add option `state` to ensure the filesystem is mounted _and_ exported
a002181 Fix typo
4a3feb9 If hadoop_tar_url variable is defined, an installation will be performed using a tar file downloaded from {{hadoop_tar_url}} instead of using the deb files defined in `deburl` or `rpmurl`.

git-subtree-dir: elasticluster/providers/ansible-playbooks
git-subtree-split: f4141ea705461e1eb2ab6fc3cbe037e59f309ab7
Add new command `gc3-config` to create a configuration file for gc3pie
Bugfixing
Add support for sge clusters.
Squashed 'elasticluster/providers/ansible-playbooks/' changes from f4141ea..e6e9837

e6e9837 Fix gridengine on CentOS: error while trying to export a directory *before* nfs server was installed.

git-subtree-dir: elasticluster/providers/ansible-playbooks
git-subtree-split: e6e983795dcbc5e7cbd4cea2d59659a467681355
Merge commit '4f2dafcc8152ad7883e20f2f1f722c8e6911ad85'
Add argument `include_config_dirs` to `Configurator.fromConfig` and move lookup of config directories to `Configurator` class
Fix ImportError while building the documentation
Add documentation for `<class>_min_nodes` option