Install Gradle with gradle binaries

Download gradle-1.10-bin.zip distribution from gradle web site, add
/path/to/gradle-1.10/bin to PATH environment variable. Don't use Gradle
Wrapper.
 Refined crosswalk embedded AAR document

 Worked on instructions being more clear
 Edited code/command blocks to ensure they appear as code
Merge branch 'fujunwei-refine_mark_aar'