fix(doc-gen): use the correct lodash method in dgeni processor (indexBy --> keyBy)

The `indexBy()` method was renamed to `keyBy()` in lodash v4 (see
lodash/lodash@b1d52cc). This commit
updates all usages of `indexBy()` to `keyBy()`.

Author: gkalpak

docs/config/processors/keywords.js

@@ -47,13 +47,13 @@ module.exports = function generateKeywordsProcessor(log, readFilesProcessor) {
 
       }
 
-      areasToSearch = _.indexBy(this.areasToSearch);
-      propertiesToIgnore = _.indexBy(this.propertiesToIgnore);
+      areasToSearch = _.keyBy(this.areasToSearch);
+      propertiesToIgnore = _.keyBy(this.propertiesToIgnore);
       log.debug('Properties to ignore', propertiesToIgnore);
-      docTypesToIgnore = _.indexBy(this.docTypesToIgnore);
+      docTypesToIgnore = _.keyBy(this.docTypesToIgnore);
       log.debug('Doc types to ignore', docTypesToIgnore);
 
-      var ignoreWordsMap = _.indexBy(wordsToIgnore);
+      var ignoreWordsMap = _.keyBy(wordsToIgnore);
 
       // If the title contains a name starting with ng, e.g. "ngController", then add the module name
       // without the ng to the title text, e.g. "controller".

docs/config/processors/pages-data.js

@@ -224,7 +224,7 @@ module.exports = function generatePagesDataProcessor(log) {
         .map(function(doc) {
           return _.pick(doc, ['name', 'area', 'path']);
         })
-        .indexBy('path')
+        .keyBy('path')
         .value();
 
       docs.push({