add app subscribe

subscribe --uri http://xxx.com.s/rss2.xml

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add application doc_fetcher

doc_fetch --uri http://sdfasdf.com/item

doc_fetcher will download all the original html/doc
add application entry_fetcher

entry_fetcher --uri http://www.sdfsad.com/rss2.xml

entry_fetcher will fetch current rss items of --uri
cleanning code
cleanning code

- remove some log messages
- use atom.Body to replace atom.Lookup..."body"
- add feature CleanFragment. CleanFragment will clean a piece of html
use HttpCleaner algorithm
redefine FetchUrl2

- FetchUrl2 will return content-type. content-type like application/xml
can be used later for determining doc format
- set http dial time to 8 seconds. fetching url from blocked website
should encounter a very long waiting time
- try a second chance to download url via goagent proxy.
- add feature FetchUrl3. FetchUrl3 will return error nor panic the error
redefine Insert.... functions

- use Upsert to insert Channel and Entry
- add feature SaveEntries
- filter entries by link/guid/title
- sort top-entries by -created, nor pubdate
- top-entries will only return unread entries
- add feature EntriesContentUnready
- add feature EntryUpdateContent, EntryUpdateContent save the full-text
doc file path to field entry.content_path
- alter MarkRead....
- remove Channel Entry's explicit _id struct memeber
remove hash function

- description and content should be the same if they are very sample, so
we hash content shouldn't work properly
- add Entry.Created field
- add ContentStatus and ContentPath fields
- rename PreSave to PreProcess
- clean Entry.summary and Entry.Content
refine FetchUrl2

- FetchUrl2 returns content-type
rename demo/main.go to demo/demo.go
remove boilerpiper_test.go
remove readabilitier_test.go
rename extractd/main.go to extractd.go
remove main.go
rename subscribe/main.go to subscribe.go
rename files
remove comments
refine FetchURl2