Add docs about read-only transactions.

[danielmai]

This change is 

[martinmr]

Reviewable status: 0 of 1 files reviewed, 1 unresolved discussion (waiting on @danielmai)

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README.md, line 124 at r1 (raw file):

`client.query()` uses a read-only transaction to execute the query.

I don't think you need two blank lines here.

[martinmr]

just remove that extra line.

Reviewable status: 0 of 1 files reviewed, 1 unresolved discussion (waiting on @danielmai)

[coveralls]

Pull Request Test Coverage Report for Build 90

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage remained the same at 94.898%

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Files with Coverage Reduction	New Missed Lines	%
pydgraph/util.py	1	90.91%

Totals
Change from base Build 86:	0.0%
Covered Lines:	186
Relevant Lines:	196

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💛 - Coveralls

[danielmai]

Reviewable status: 0 of 1 files reviewed, 1 unresolved discussion (waiting on @martinmr)

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README.md, line 124 at r1 (raw file):

Previously, martinmr (Martin Martinez Rivera) wrote…

I don't think you need two blank lines here.

Done.