Basically this is caused by sqlite actually doesn't have any
column type restriction. also save gob type column as blob to enforce
byte-string value, since varchar with utf8 collation type will take at
least 3 byte to store, this will break YAML-Gob decoding at `params`
column.
Also fix some typo, and clean up fixtures code.
This allows the same SHA to have different builds on different branches, each
separately viewable. This is useful for expressing a "pipeline" in terms of
branches, e.g. a commit starts on branch A and progress through B and C to
master, with the build script switching on branch name.
Previously viewing each build would arbitrarily choose which branch's commit
to show.
