chore: revise module path & adopt ostracon, line/tm-db/v2 (#13)

* chore: revise module path & adopt ostracon, line/tm-db/v2

* chore: add circleci config.yml

* fix: lint errors

* chore: revise path in Makefile

[skip ci]

* chore: revise path in Makefile

* chore: go env & git config in circleci/config.yml

* chore: revise .circleci/config.yml

* reorder `git config` & `go get`
* reorder `lint`, `test`

fix: fix to check the negative cache size (#11)

* fix: fix to check the negative cache size

* chore: add a metric for node db cache size

feat: add promethues metrics for cache hits and misses (#2) (#7)

fix: make GetVersioned available after doing LazyLoadVersion (#6)

* fix: make GetVersioned available after doing LazyLoadVersion

* fix: apply comment; make HasRoot function

* fix: apply comment; VersionExists may update versions

* fix: apply comments; modify variable name

* fix: apply comment; use VersionExists to check version

* fix: lint error

* fix: apply comment; move a line

fix: make GetVersioned available after doing LazyLoadVersion (#6)

* fix: make GetVersioned available after doing LazyLoadVersion

* fix: apply comment; make HasRoot function

* fix: apply comment; VersionExists may update versions

* fix: apply comments; modify variable name

* fix: apply comment; use VersionExists to check version

* fix: lint error

* fix: apply comment; move a line

changelog: release 0.15.0 (#335)

changelog: release 0.14.3 (#333)

changelog: release 0.15.0-rc5 (#331)

changelog: release 0.15.0-rc4 (#323)

changelog: release 0.14.2