Drop support for Python2.6

[jaimebuelta]

Python 2.6 was released in 2008, so I think is safe to remove (it still supports 2.7), allowing some cleaning of the code.

[codecov]

Codecov Report

Merging #28 into master will increase coverage by 0.93%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #28      +/-   ##
==========================================
+ Coverage   96.58%   97.52%   +0.93%     
==========================================
  Files           1        1              
  Lines         205      202       -3     
==========================================
- Hits          198      197       -1     
+ Misses          7        5       -2

Impacted Files	Coverage Δ
ffind/ffind.py	97.52% <100%> (+0.93%)	⬆️

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[coveralls]

Coverage increased (+0.9%) to 97.015% when pulling 2fca28c on drop_support into a30b539 on master.

[coveralls]

Coverage increased (+0.9%) to 97.015% when pulling 2fca28c on drop_support into a30b539 on master.

[coveralls]

Coverage increased (+0.9%) to 97.015% when pulling 2fca28c on drop_support into a30b539 on master.

[coveralls]

Coverage increased (+0.9%) to 97.512% when pulling aa177fc on drop_support into 88bd861 on master.

[coveralls]

Coverage increased (+0.9%) to 97.512% when pulling f07ea99 on drop_support into 88bd861 on master.

[coveralls]

Coverage increased (+0.9%) to 97.525% when pulling 9072965 on drop_support into 6b70416 on master.