update customized bootstrap
  * adjust 'Common CSS'
comment zsd.css
add doctype to html
add new directives
  * zsd-show-if-defined
  * zsd-show-if-empty
show message if no snapshots found
FileUtils work on a given 'fileInfo'
  * for every FileUtils call was a get request to the server
fixed size for binary content in view
  * FIXME: needs rework!
  * currently a fixed size is set
refactor directive: zsd-file-actions
  * code cleanup
  * decrease unecessary requests to the server
    (was 3 per file - even the server respons with not-found)
use phantomjs for testing
messages per directive: notifications
  * messages saved as array - no messages get lost
  * autoremove after given timeout
   (in index.html where the directive is used)
convert server error response when it is a blob
  * when binary content are requested, the response has type blob
  * error response messages needs to be converted to text
fix directive zsd-embed-src
  * prefix 'zsd' was missing in html and js
  * bugfix for commit: 26a527275a2cda412791c4ab45d7d4bb8366f10b
FrontendConfig as map[string]interface{}
  * config keys in lower case
  * simpler to add new configs
limit scan snapshots for file-modification (off by default)
  * scan for file-modifications are io bound
  * per snapshot one file stat cmd (when mod-time / size are checked)
  * if the given limit is negative (default) all snapshots are scannend
method to determine if file has changed configurable
  * currently supported: size+modTime, size or md5
update README