Deactivate bad unused import.

* ebaysdk missing from project requirements.
Enable pylint imports check (F0401).
Do not pylint inside html/bower_components.
Subpackage db and test folders.

* Effectively allows relative imports from/to these folders.
Fix broken imports in the db, features and test packages.
Locally disable import errors.

* Unable to import distutils.utils in Travis CI.
Merge pull request #665 from Renelvon/sane_imports

Install package structure. Fix imports (part 1). Enable pylint flag F0401.
Disallow wildcard imports (W0401).

* Also flag unused names from wildcard imports (W0614).
Refactor wildcard imports.

* Drop wildcard; state imported names explicitly.
* Import each module only once.
* Drop unused imports.
* Fix broken imports: Explicitly import modules
  previously implicitly imported by wildcard.
Merge pull request #673 from Renelvon/no_wildcard_imports

Fix imports (part 2). Disallow wildcard imports (W0401, W0614)
Upgrade to pybitcointools 1.1.15.
Merge pull request #691 from Renelvon/bump_pybitcointools

Upgrade to pybitcointools 1.1.15