Skeleton docs

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Extremely basic docs

E.g. no listing of individual fixers yet, but at least the basic
structure is there.
List all 2to3 fixers
Document opt-in fixers
Document six fixers
Doc independent fixers
fix_raise can subclass 2to3 fixer
Fix test for six imports mapping
.travis.yml: install a recent version of six, since some tests depend on it.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
Merge pull request #82 from takluyver/fix-raise-subclass-2to3

Subclass FixRaise from 2to3
Correct the doc comment for fix_next.py.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
Remove unused imports.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
Cosmetics.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
Proposed tests for fix_import.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
Fix addition for __future__.absolute_imports by fix_import

The 2to3 fixer makes no changes if it guesses that all the imports are
absolute. We still want to add absolute_import in that case, however.
Make __future__ import check more robust
Update fix_imports_six tests for addition of absolute_import
Use our own touch_import in fix_int_long_tuple, so absolute_imports is added
Merge pull request #86 from python-modernize/85-test-fix-import

Tests for fix_import; also change the fixer to add 'from __future__ import absolute_import' even if the 2to3 fixer makes no changes.
Don't do a redundant idempotence check if it's the same as the output check we just did.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>