Migrate to flake8

Working on Turpial/libturpial#33 issue. Until now we covered
the following tasks:

- [x]      E501 line too long
- [x]      E302 expected 2 blank lines, found 1
- [x]      W291 trailing whitespace
- [x]      W391 blank line at end of file
- [x]      E128 continuation line under-indented for visual indent
- [x]      F401 imported but unused
- [x]      F403 unable to detect undefined names
- [x]      E127 continuation line over-indented for visual indent
- [x]      E231 missing whitespace after ':'
- [x]      W601 .has_key() is deprecated, use 'in'
- [x]      E251 unexpected spaces around keyword / parameter equals
- [x]      E303 too many blank lines (2)
- [x]      E126 continuation line over-indented for hanging indent
- [x]      W293 blank line contains whitespace
- [x]      E301 expected 1 blank line, found 0
- [x]      E261 at least two spaces before inline comment
- [x]      E711 comparison to None should be 'if cond is not None:'
- [x]      E203 whitespace before ':'
- [x]      E701 multiple statements on one line (colon)
- [x]      E225 missing whitespace around operator
- []       F841 local variable is assigned to but never used
- []       F821 undefined name
- []       F999 syntax error in doctest
Some improvements to send_tweet example

- [x] Handling the exception when libturpial is not in the sys.path
- [x] Now it's possible to parse arguments from the command line
- [] Support for identi.ca protocol
Migrate to flake8
Added warnings and todos. Fixed minor issue
Finished Core testing
Started (uncomplete) account manager testing
Finished column manager testing
Finished status.py test
Finished column.py tests
Finished list.py tests
Added tests for exceptions
Fixed exception tests. Added common.py tests
Added tests for tools
Added more tests to account manager
Removed logs, supported default params, added #TODO comments
Working on config tests
Added tests for proxy model
Added tests for profile model
Added tests for short url adapter
Added tests for generic service