Dvc

* dvc: make flufl.lock opt-in and use zc.lockfile (2918) efiop
* test: a couple of dir helpers fixes (2938) Suor
* checkout: test: refactor to dir helpers (2934) pared
* commit: test: refactor to dir helpers (2932) pared
* snap: remove plugs (incompatible with classic) (2939) casperdcl
* use cache dir as a default remote when importing from local repo (2915) maykulkarni
* import-url: add directories to examples (2907) efiop
* test: move: convert to dir helpers (2926) pared

* add: test: convert to dir helpers 3 (2921) pared
* get: refactor, clean up and fix `dvc get` implementation (2925) Suor
* build_deb: Debian directory appended. Issue 2800 (2924) Abrosimov-a-a
* get: copy/download files tracked by Git (2837) danihodovic
* test: write a usage text for dir_helpers (2908) Suor
* analytics: refactor into a module (2826) mroutis
* test: migrate test_ignore (2913) Suor
* add: test: convert to dir helpers 2 (2906) pared

* dvc/dagascii: Use pager instead of AsciiCanvas._do_draw (2815) xliiv

* remote: base: download: don't walk dir twice (2909) efiop
* add: test: convert to dir helpers 1 (2898) pared
* import-url: support directories (2894) verasativa

Fixed pypi package deployment.

* dvc: revert checkout to be silly and fast, relink on dvc add though (2882) Suor
* test: refactor tmp dir helper fixtures (2868) Suor
* state: quote % in path (2892) efiop
* external repo: checkout revision before initializing dvc repo (2852) pared
* much grammar such fix (2883) casperdcl
* lengthen bars unless nested/threaded (2857) casperdcl
* Stream progress (2875) casperdcl
* NoRemoteInExternalRepoError: fix message (2881) pared
* Snap (2778) casperdcl
* Support adding directories in google cloud storage remote (2853) skshetry
* s3: Check for all files in given path to match (2873) skshetry
* test: skip non supported remotes fast in api tests (2870) Suor
* GDrive remote support (2551) MaxRis
* s3: ignore empty directories while walking files (2683) mroutis
* remote: http: raise exception when response with error status code (2794) pared
* remote: protect all remote client/session creation code with locks (2863) Suor
* test: refactor & remove redundant test fixtures (2861) danihodovic
* perf: optimize cache listing for local, ssh and hdfs (2836) Suor
* remote: small .save_info()/.get_checksum() cleanup (2835) Suor
* RemoteNotSpecifiedInExternalRepoError: dont pass cause of exception (2854) pared