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
Fixed version number
Merge branch 'development' of https://github.com/Turpial/libturpial into development
Added more patterns of untracked files to ignore.
Added initial support for Travis-CI.
Added support for sphinx_rtd_theme, it's awesome.
Added the Travis-CI and Coveralls badges.
Fixed documentation errors.
Added extra info to media object from preview images
Merge pull request #37 from milmazz/development

Continuous integration
Merge remote-tracking branch 'turpial/development' into development
Updated travis badges and changelog
Modified protocol test. Removed py33 from tox. Updated badges urls
Modified protocol test to avoid error due to localtime
Recovered PR from @milmazz from 8 months ago
Recovered PR from @milmazz from 8 months ago (part 2)
Fixed issues when merging @milmazz changes
Fixed issue when registering new config options