CB-13573: Clarify Cordova Android 6.4.0 blog post
CB-13573: Clarify Cordova Android 6.4.0 blog post

- add link to gradle install instructions
- add link to crosswalk project and issue (I created for this)
- reword and restructure text a bit
stevengill/cordova-docs,apache/cordova-docs,shazron/cordova-docs,apache/cordova-docs,stevengill/cordova-docs,shazron/cordova-docs,apache/cordova-docs,purplecabbage/cordova-docs,shazron/cordova-docs,purplecabbage/cordova-docs,stevengill/cordova-docs,stevengill/cordova-docs,purplecabbage/cordova-docs,purplecabbage/cordova-docs,shazron/cordova-docs,apache/cordova-docs