WIP: huge error handling refactoring
Minor cleanups
Merge branch 'dev'

Conflicts:
	src/base.rs
	src/traits.rs
Minor module adjustments
Shortcut to EnvBuilder through Environment::new()
Update .travis.yml
WIP: API rethinking
Updated docs

As rust-ci.org always returns and mystic error, now docs are
uploaded to GitHub pages instead using Alex Crichton trick
Further tuning up-doc script
Merge branch 'master' into wip
General overview docs & stability marks
Better flags doc lines
static -> const + enable non snake statics
Fixed warnings in tests
Allow to implement conversion traits
At least a couple of words about traits
Saner items API names
Minor test updates
CursorItemIter fixes

- `pos` wasn’t used anywhere anyway

- added unwrapping
Fixes in iterator size hints

Both KeyRange and Cursor iterator actually don’t know anything about bounds (to be precise - their estimation is number of keys in database, which could be huge, so we’re ignoring them for now).

Only Item iterator can give a correct number after it was pointed to correct key. Note: pointing to key happens only after first access.