Hide output in io-code-block by default (#322)

* Hide output by default

Author: Chris Cho

source/quick-reference.txt

@@ -32,6 +32,7 @@ their related reference and API documentation.
 
           .. output::
              :language: js
+             :visible: false          
 
              { title: 'Hamlet', type: 'movie', ... }
 
@@ -51,6 +52,7 @@ their related reference and API documentation.
 
           .. output::
              :language: js
+             :visible: false
 
              [
                { title: 'Christmas in Boston', year: 2005, ... },
@@ -102,6 +104,7 @@ their related reference and API documentation.
 
           .. output::
              :language: js
+             :visible: false
 
              { title: 'Amadeus', imdb: { rating: 9.5, ... } }
 
@@ -124,6 +127,7 @@ their related reference and API documentation.
 
           .. output::
              :language: js
+             :visible: false
 
              [
                { title: 'A Beautiful Mind', year: 2001, imdb: { votes: 826257, ... },
@@ -149,6 +153,7 @@ their related reference and API documentation.
 
           .. output::
              :language: js
+             :visible: false
 
              { title: 'Cosmos', genres: [ 'Documentary', 'Educational' ] }
 
@@ -171,6 +176,7 @@ their related reference and API documentation.
 
           .. output::
              :language: js
+             :visible: false
 
              { name: 'Lord of the Wings', zipcode: 10001 }
 
@@ -225,6 +231,7 @@ their related reference and API documentation.
 
           .. output::
              :language: js
+             :visible: false
 
              BulkWriteResult {
                result: {
@@ -260,6 +267,7 @@ their related reference and API documentation.
 
           .. output::
              :language: js
+             :visible: false
 
              [
                { title: '2001: A Space Odyssey', ... },
@@ -283,6 +291,7 @@ their related reference and API documentation.
 
           .. output::
              :language: js
+             :visible: false
 
              [
                { title: '2001: A Space Odyssey', ... },
@@ -305,6 +314,7 @@ their related reference and API documentation.
 
           .. output::
              :language: js
+             :visible: false
 
              618
 
@@ -323,6 +333,7 @@ their related reference and API documentation.
 
           .. output::
              :language: js
+             :visible: false
 
              [ 1891, 1893, 1894, 1896, 1903, ... ]
 
@@ -341,6 +352,7 @@ their related reference and API documentation.
 
           .. output::
              :language: js
+             :visible: false
 
              [
                { title: 'My Neighbor Totoro', ... },
@@ -362,6 +374,7 @@ their related reference and API documentation.
 
           .. output::
              :language: js
+             :visible: false
 
              [
                { title: 'Rocky III', ... },
@@ -384,6 +397,7 @@ their related reference and API documentation.
 
           .. output::
              :language: js
+             :visible: false
 
              [
                { title: 'Newark Athlete', year: 1891, ... },
@@ -407,6 +421,7 @@ their related reference and API documentation.
 
           .. output::
              :language: js
+             :visible: false
 
              [
                { year: 2012, imdb: { rating: 5.8, votes: 230, id: 8256 }},
@@ -440,6 +455,7 @@ their related reference and API documentation.
 
           .. output::
              :language: js
+             :visible: false
 
              [
                { title: 'The Life Aquatic with Steve Zissou', ... }