converted commands to be classes
Merge branch 'master' into commands_as_classes

Conflicts:
	parser/parser.go
Added mail tests
Reorganized file
Added session which is created on Selected state. Allow Selected -> Selected transition. Do not pass mail proxy in constructor.
added log line
Added Literal response type
No longer send mail proxy to connection state constructor
Converted to use ImapCommands. Ran gofmt.
do not pass mailproxy to constructor
reorganize file, refactored around ImapCommands
added mail package. Added base Maildir implementation.
support fetch ranges via SequenceSet. still needs parser support