style(core): new indenting style
feat(core): add markdown service, filter and preview directive

Correlated with #18
chore(core): update gulp-load-plugins version
style(preview): inline code fixes
style(core): change preview style for syntax
fix(gen): add plumber and remove unwanted map files

Little gulpfile refactor.

Related with #18.
fix(core): prevent convert when input is null

Linked with #18.
test(core): add new tests for preview and filter
refactor(gen): remove gulp-util
refactor(test): change bullet list test
refactor(gen): change build process
refactor(core): update devDependencies
fix(test): prevent incorrect passing builds
test(e2e): change chromedriverpath and use only chrome
test(e2e): refactor and reset to sauce
test(e2e): change spaces
test(e2e): refactor protractor basics
chore(core): bump package version
docs(core): new readme version for 2.4.0
Merge branch 'release/2.4.0'