Linter shouldn't depend on `sentry` being installed

bin/lint

@@ -1,8 +1,11 @@
 #!/usr/bin/env python
 from __future__ import absolute_import
 
+import os
 import sys
 
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), os.pardir, 'src'))
+
 from sentry.lint.engine import check_files
 
 offset = 1