testing (docs) preserve stack trace

[stephenplusplus]

This preserves the original error from the "VM" that runs the examples from our docs.

It also tests each method individually as opposed to testing each file. Each file contains several methods, and if any one of them throws, to help track down the offending line, all of the example code from all of the methods was displayed. It now only displays the code from the example that threw. Additionally, it stops printing the lines from the example that threw after the offending line.

To test, I changed bigquery#createTable to always throw an error: "Must be 7".

Before

  10) documentation should run tests for docs/json/master/bigquery/dataset.json without errors:
     Error:
var gcloud = require('../');

var bigquery = gcloud.bigquery({
  keyFilename: '/path/to/keyfile.json',
  projectId: 'grape-spaceship-123'
});
var dataset = bigquery.dataset('institutions');
dataset.create(function(err, dataset, apiResponse) {
  if (!err) {
    // The dataset was created successfully.
  }
});
dataset.exists(function(err, exists) {});
dataset.get(function(err, dataset, apiResponse) {
  if (!err) {
    // `dataset.metadata` has been populated.
  }
});
dataset.getMetadata(function(err, metadata, apiResponse) {});
var metadata = {
  description: 'Info for every institution in the 2013 IPEDS universe'
};

dataset.setMetadata(metadata, function(err, apiResponse) {});
var tableId = 'institution_data';

var options = {
  // From the data.gov CSV dataset (http://goo.gl/kSE7z6):
  schema: 'UNITID,INSTNM,ADDR,CITY,STABBR,ZIP,FIPS,OBEREG,CHFNM,...'
};

dataset.createTable(tableId, options, function(err, table, apiResponse) {});
dataset.delete(function(err, apiResponse) {});
dataset.delete({ force: true }, function(err, apiResponse) {});
dataset.getTables(function(err, tables, nextQuery, apiResponse) {
  // If `nextQuery` is non-null, there are more results to fetch.
});
dataset.getTables()
  .on('error', console.error)
  .on('data', function(table) {})
  .on('end', function() {
    // All tables have been retrieved
  });
dataset.getTables()
  .on('data', function(table) {
    this.end();
  });

var institutions = dataset.table('institution_data');

must be 7
      at runCodeInSandbox (test/docs.js:37:11)
      at Function._throws (assert.js:306:5)
      at Function.assert.doesNotThrow (assert.js:337:11)
      at Context.<anonymous> (test/docs.js:112:14) 

After

  1) documentation should run tests for bigquery/dataset.js#createTable without errors:

var tableId = 'institution_data';
var options = {
  // From the data.gov CSV dataset (http://goo.gl/kSE7z6):
  schema: 'UNITID,INSTNM,ADDR,CITY,STABBR,ZIP,FIPS,OBEREG,CHFNM,...'
};
dataset.createTable(tableId, options, function(err, table, apiResponse) {});

must be 7
  Error: must be 7
      at Dataset.createTable (lib/bigquery/dataset.js:196:9)
      at assert-code.vm:8:9
      at ContextifyScript.Script.runInNewContext (vm.js:18:15)
      at Object.exports.runInNewContext (vm.js:49:17)
      at runCodeInSandbox (test/docs.js:32:8)
      at Function._throws (assert.js:306:5)
      at Function.assert.doesNotThrow (assert.js:337:11)
      at Context.<anonymous> (test/docs.js:125:16)

[stephenplusplus]

Going to try to add something else in here that might make it more helpful. Please hold!

[coveralls]

Coverage remained the same at 100.0% when pulling 14cf805 on stephenplusplus:spp--doc-test-stacktrace into c6d6bc3 on GoogleCloudPlatform:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 7d386a1 on stephenplusplus:spp--doc-test-stacktrace into ccc8dcf on GoogleCloudPlatform:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 7d386a1 on stephenplusplus:spp--doc-test-stacktrace into ccc8dcf on GoogleCloudPlatform:master.

[callmehiphop]

So goood!