Update .gitignore
Updated to force installation of argparse

closes #138
Add documentation, fix missing args.

Added `--all-indices` option to snapshot args
Added missing `--snapshot-prefix` arg
Improve documentation
Massive refactor and rearranging of code + docs

Methods were moved around to group them together.
Documentation was updated for each method to use Sphinx style
A *major* refactor of the snapshot methods was undertaken.  Now incrementals are supported.
A few code fixes were introduced to make the methods more consistent.
Make es_repo_mgr more in line with API changes

Documentation and method changes to make things work better and more clearly.
Major refactor to reflect changes to curator.py

Properly tests after the changes to the snapshot functionality in curator.py
Added sphinx documentation to the project
Fix missing month check in validate_timestring()

closes #158
Remove CHANGELOG in favor of Changelog.rst
Update with recent bug fix and contributor info
Changes reflect method renaming in es_repo_mgr.py