Warn/raise error when config file is inaccessible

Fixes grnet/kamaki#71

Raise an error if the file is not readable or not existing, warn if
it is not writable, add a description to the error message when
kamaki attempts to write to a non-writable config file.
Handle non-ascii characters in config files

Fixes grnet/kamaki#76

* Support non-ascii characters for all values
* Disallow non-ascii characters for all types of options
* Escape control characters in option names and values
Handle SSL unicode bug with grace

Fixes grnet/kamaki#67

SSL module breaks when dealing with non-ascii filenames (known bug).
Catch the Unicode error when it occurs and add an instructive error
message for the kamaki library users.
Check the file name for validity when it is set and inform the kamaki
CLI users.
Escape logged HTTP data before token replacement

Problem: when LOG_DATA is on and LOG_TOKEN is off, kamaki logs HTTP
data, replaces the token (if it is included in the data) and then
escapes them to prepare for safe logging. If the data is non-ascii,
replacing raises a unicode error.

Solution: escape data before replacing the token.
Check server status before changing it

Fixes grnet/kamaki#57

This fix affects the CLI commands "server_start", "server_reboot"
and "server_shutdown" which are specified in "kamaki.cli.cmds.cyclades".
These are the operations that modify the status of a server.

The problem was caused when the target status was the same as the current.
In this case, the request for status modification would fail with a 400
error code response. At this point, kamaki couldn't have adequate information
to correctly evaluate the error.

This problem is solved by checking the current status before attempting to
modify it.  Also, the server ID is validated in advance, instead of waiting
for a 400 server error.
Update general information and setup instructions

Refs grnet/kamaki#49
Write a set of short scripts using the kamaki lib

Fixes grnet/kamaki#49
Return volume metadata in "create_volume"

The method used to return results in this format:
  {"volume": {"id": ..., "display_name" ..., ...}}
It now returns the results in this form:
  {"id" ..., "display_name" ..., ...}
as it is the case with every other creation command in kamaki library.
Support old history files

Fixes grnet/kamaki#80

Kamaki history files must have an offset counter on the first line,
since version 0.11.

With this fix, kamaki supports older history files and adds the
default offset counter at the first line.
Fix pithos client tests and pep8 errors
Update Changelog with release date for 0.13rc6
Merge branch 'release-0.13' into debian-release-0.13
Bump version to 0.13~rc6-1~wheezy

Signed-off-by: Ilias Tsitsimpis <iliastsi@grnet.gr>