Add stream option to limit memory consumption (fixes #162, #188)

[Toilal]

[Toilal]

1 hour later, TravisCI is still pending :(

[codecov[bot]]

Codecov Report

Merging #608 (45499bf) into master (23d2993) will decrease coverage by 0.14%. The diff coverage is 89.02%.

@@            Coverage Diff             @@
##           master     #608      +/-   ##
==========================================
- Coverage   96.82%   96.68%   -0.15%     
==========================================
  Files          20       20              
  Lines        1514     1570      +56     
==========================================
+ Hits         1466     1518      +52     
- Misses         48       52       +4     

Impacted Files	Coverage Δ
sqlparse/__init__.py	92.85% <83.33%> (-7.15%)	:arrow_down:
sqlparse/lexer.py	91.66% <89.06%> (+5.95%)	:arrow_up:
sqlparse/engine/filter_stack.py	100.00% <100.00%> (ø)
sqlparse/engine/statement_splitter.py	100.00% <100.00%> (ø)
sqlparse/sql.py	97.62% <100.00%> (+0.02%)	:arrow_up:

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