Refactor bolt commands into individual files.
Merge pull request #97 from benbjohnson/cli

Refactor bolt commands into individual files.
Add DB.Check().
Merge pull request #98 from benbjohnson/fsck

Add DB.Check().
Write freelist after each commit.

Well, this is embarassing. Somehow the freelist was never getting written after each commit.
This commit fixes that and fixes a small reporting issue with "bolt pages".
Merge pull request #102 from benbjohnson/fix-freelist

Write freelist after each commit.
Remove DB.Open() and only allow bolt.Open().

Per @tv42's suggestion, this commit removes the ability to reopen an
instance of DB. All open calls go through bolt.Open().

Fixes #103.
Merge pull request #104 from benbjohnson/remove-db-open

Remove DB.Open() and only allow bolt.Open().
Add DVID to projects using Bolt

DVID added Bolt as an optional storage engine.
Merge pull request #107 from DocSavage/master

Add DVID to projects using Bolt
Remove count and overflow columns for free pages on 'bolt pages'.

The count and overflow columns are meaningless for freed pages since
there could be random overflow data in there. This commit removes those
columns for free pages.
Merge branch 'master' of https://github.com/boltdb/bolt
README

Remove the 'Internals' section since it is half-assed right now.
Consolidate file and metafile descriptors.

Previously, a two file descriptors were used for the database: file & metafile. The "file" file
descriptor was used for async writes while the "metafile" file descriptor was used with O_SYNC
writes. This commit changes that so that there's only one file descriptor and it uses fdatasync()
to synchronize writes.
Merge pull request #109 from benbjohnson/consolidate-file-descriptors

Consolidate file and metafile descriptors.
Add advisory file locking.

This commit adds advisory locking via flock() to the database file. This ensures that two separate
processes cannot both open the same data file which would cause corruption.

Fixes #110.
Merge pull request #111 from benbjohnson/flock

Add advisory file locking.
Add performance counters.

This commit adds performance counters for each transaction which are rolled
up to the database level on each commit/rollback. Counters are meant to be
a very fast way to track what is going on in the database. A few timers are
also added in areas where the time.Now() overhead is not noticible.

The DB.Stat() function is now deprecated since the `bolt` CLI now performs
similar functions.

Fixes #108.
Merge pull request #112 from benbjohnson/perf-stats

Add performance counters.
Add meta page checksums.

This commit adds checksums to the meta pages on every write. When the
database loads, it verifies the checksums on the meta pages and returns
an error if either one is corrupt.

In the future, it should fallback to the previous meta page but for right
now it just hard fails. This is at least preferable to opening the database
and getting a random error or further corruption.

Fixes #25.