Add Console-script, sql.Operation, fix examples

[vmuriart]

• Uses console-scripts/entry-points for sqlparse script. Closes Add extension .py to bin/sqlparse #247, Closes Can't get sqlformat into path #220
• Adds sql.Operation grouping. Closes Group mathematical equations akin to comparisons? #211
• Fix examples, closes example doesn't work #168. closes Example column_defs_lowlevel.py fails  #129

Needs to add tests for sqlparse cli script. Decreases coverage by 3% 😢

[coveralls]

Coverage decreased (-3.7%) to 93.303% when pulling 42fb1d0 on vmuriart:console-script-examples-sqlOperation into 50de51a on andialbrecht:master.

[codecov-io]

Current coverage is 93.30%

Merging #255 into master will decrease coverage by 3.69%

@@             master       #255   diff @@
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  Files            20         21     +1   
  Lines          1265       1314    +49   
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
- Hits           1227       1226     -1   
- Misses           38         88    +50   
  Partials          0          0          

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[vmuriart]

From 97% to 93.3% 😢.

[andialbrecht]

@vmuriart the sqlformat script wasn't included in coverage before ;)