(#583) - compact callback after compaction's done

Now http adapter behaves like others. The code manually pings
database to check if it's done compaction.
(#583) - uncomment compaction test

This test was failing due to http compaction took some time
and callback was fired before it finished. Now it's fixed
(#583) - add compaction documentation
(#583) - ping remote server correctly

Better now:
1. starting pinging _after_ the compaction started
2. try again _only_ if we got answer
Merge pull request #617 from neojski/583-call-compact-callback-when-done

(#583) - call compact callback when done
(#538) - Switch to Linux to test Firefox

I did a review of the bulk_docs code and cannot see where
our tests could intermittently fail, this seems to be a
quirck with FileReader on windows. Linux tests have been
far more stable.

I also removed some redundant error handling code and
unneeded backwards compatibility code
Merge pull request #619 from daleharvey/attach-tests

(#538) - WIP testing if linux is more stable
(#611) - move opts cloning to generic adapter

That is: get rid of extend in specific adapters as it can be done in
generic one. Also - use new Pouch.error method
(#300) - Add id to stored revsisions to ensure uniqueness

Thanks to @neojski for the test and @trokster for the original
implementation of the fix.
(#577) - Initial implementation of auto-compaction
Fix linting errors
(#623) - Switch to self hosts couchdb for test results
(#578) - enable local adapters in test.issue211.js

Also:
* compaction now fires callback when it's finished so #280 looks
no longer needed
* remove empty braces in get which looked like some legacy
* replace ok with strictEqual
(#578) - fix linting error
(#563) - Remove feature detection for compaction in tests
(#612) - Add seperate travis test target
(#628) - Added Pouch.enableAllDbs flag to make allDbs optional
(#628) - updated allDbs tests (enable allDbs for the particular tests)
Merge pull request #631 from daleharvey/628-changes-to-allDbs

changes to all dbs
(#579) - Merge rev_map into rev_tree