Fix HTML closing errors
Open invitation setting

Closes #64
Fixup signup and settings template
fix for #70 to prevent caching build images
Fixup behavior on uninstalled state
Migration Driver for SQLite

Need more tests.
Integrate MigrationDriver to migrate.go
Fix migration step not checked against current version.

Add tests for DropColumns.
More tests for alter columns migration

Also change the way we handle columns rename migration.
SQLite restrict column addition not to have PRIMARY KEY and/or
UNIQUE attribute, so we have to change from:

add new column -> migrate data from old column to new column ->
rename old table -> create new table with old columns removed ->
migrate data from old table to the new table -> drop old table

to directly:
rename old table -> create new table with renamed columns ->
migrate data from old table to the new table -> drop old table
Add tests to migrate existing database without migration attributes.
Integrate migrations with drone.

Also add migration to tests.
Merge remote-tracking branch 'origin/master'
Merge pull request #67 from floatdrop/open-invitations

Open invitation setting
Merge remote-tracking branch 'origin/master'
added code to prevent panic if /login is reached but no settings exist
minor styling. added success and fail message to top of /signup screen
modified open_registration to boolean value in database
make run now puts db in pwd, not /tmp. got sick of starting from scratch
Merge pull request #33 from phusion/master

Fix HTML closing errors
Added GitHubApiUrl and GitHubDomain to settings and template
Put values from settings into handler/auth.go
Use custom github domain for webhook