Add some missing comments.

ok @davecgh
Add vet and lint where possible to travis.
Error improvements for lint.

Rename errors to Err*.
Lowercase error text.

Add golint for top level package

ok @davecgh
Fix tests.
Update ldb tests for latest API error changes.
Changed TxIn.PreviousOutpoint to TxIn.PreviousOutPoint after btcwire API change.
IMPORT PATH MODIFICATION CHANGESET
----------------------------------

Please use this changeset as the first one on top of the conformal codebase.
Note that if there are new imports, they need to be changed as part of this
changeset. In general, use "git rebase" on github.com/conformal's version
and apply this changeset first.