update dependencies
Add badges
Update ESLint configuration
Update to esutils@1.1.6
Update URLs
Merge esotope's benchmark suite into escodegen

ref #211
Add esotope dependencies into benchmark suite
Make benchmark suitable for escodegen

Make benchmark script suitable for escodegen.
Fix eslint settings
Extract big switch to Statement CodeGenenerator
Extract option variables into local variables
Move generateExpression's big switch to CodeGenerator's prototype
fix missing link in README.md
Merge pull request #212 from vvakame/patch-1

fix missing link in README.md
Add old escodegen for benchmarks
Use CodeGenerator.prototype as lookup table
Drop withIndent's call and return result

withIndent's result is not used.
Drop switch use
Remove unused variables
Add @inikulin copyrights