Made changes to the AUTHENTICATE AN ACCOUNT section under ACCOUNTS resource

+ Added a simple POST example of a successful request
+ Added explaination the value field being passed
+ Added clarification that authentication is done on the application resource

+ Modified the text for the link to more information regarding authentication under the APPLICATIONS resource
+ Modified titles in Java and Ruby from 'Authenticate Accounts' to 'Authenticate an Account'
+ Modified section in Java and Ruby to match REST docs

+ Deleted the note refering to workflows only being able to be modified by administrators
+ Deleted the Authenticate an Account section from the DIRECTORY resource section.  Authentication is not handled by the directory resource
Merge branch 'dev' of https://github.com/stormpath/stormpath.github.io into dev

Conflicts:
	source/java/product-guide/index.markdown
Merge branch 'dev' into source
Merge branch 'dev' of https://github.com/stormpath/stormpath.github.io into dev
Merge branch 'source' into dev