Fixes a bug whereby akamai parameter configuration did not work as documented:

Changed __init__.py so that it would not error on a missing .akamai file prior to checking for its existence.

In addition, changed to not Raise an exception on a missing .akami file; instead, it prints a warning indicating that the necessary kwargs must be passed into PurgeRequest() init. This satisfies the documented ability to configure the purger via environment variables, a .akamai file, or via direct arguments to PurgeRequest()
Modified README to include code sample for usage on servers requiring a proxy
Removing print of WARNING for missing Akamai credentials. The documentation clearly demonstrates the ways in which credentials can be passed into this module
Merge pull request #2 from marcesher/master

Change to initialization such that it works as documented