refactor(safari): drop Safari support

This closes #40.
feat(build): concat scripts using gulp

- remove build.sh and build.bat
- add package.json and gulpfile.js
- rename source/vkopt.js to source/01_vkopt.js and so on
to define order of concatenation since gulp.src() pipes files
in alphabetical order (this is the simpliest and best option)
- edit builds/*/inject.js accordingly

This closes #17 and #18.
feat(build): inject source as string into opera-inject.js

- add source/meta/opera-inject.js, inject source into this file using
gulp; in this file run injected source using eval(). The file is called so
to maintain consistency with other */inject.js files, because it should
inject source code into page context; not because of source string
injection
- in gulpfile concat and inject source into opera-inject.js and write
result to builds/opera/includes/inject.js

This closes #41.
feat(build): inject source as string into maxthon-inject.js

- add source/meta/maxthon-inject.js, inject source into this file using
gulp; in this file push injected source into page context using <script> tag
- in gulpfile concat and inject source into maxthon-inject.js and write
result to builds/maxthon/inject.js
- remove includeFrames: true from def.json. See: #42.

This closes #39.