Imports: remove unused in translate/convert
Imports: remove unused in setup.py
Imports: remove unused in translate/storage/versioncontrol
Imports: remove unused in translate/storage
Imports: remove unused in translate/storage
Imports: remove unused in translate/tools
Imports: remove unused in translate/filters
Imports: remove unused in translate/search/indexing
Travis: --use-mirrors is deprecated in pip 1.5
Travis: Byte compile all .py files

Attempt to catch any syntax errors that maybe aren't caught by tests. Or
that are caught in files that aren't part of the setup scripts.
Travis: run setup.py building as a check
odf2xliff: Use a real with block
xml_extract: Use a real with block
misc: Drop context.py (fake with blocks)
misc: Drop contextlib, use stdlib contextlib instead