* Add function to escape a shell argument.
* Keep track of the last used window.
* Implement support for the open-file event.
* The shell escape regex needs parentheses to be captured.
* Removed lastWindow and added getLastFocusedWindow method to app
* Create window create new session only if no callback passed
* Added app.windowCallback to handle open-file before "ready"
* Small lint fixes
* Differeent open file handling: check if it is directory, and if the file is executale or not
* Small fixed and added some comments
* Added php-escape-shell module in place of custom escapeShellArgument()
* Fixed wrong code and added detailed comment
* Aliased php_escapeshellcmd import
* Rebased; added error handling in OpenFile
* changed string contatenation with template literal
* Pinned php-escape-shell dependency
* Typo fix
* getLastdFocusedWindow now uses Array.prototype.reduce()
* Notify users of unexisting path while open file
* Step 1: move electorn into `app/`.
This is to comply with the suggested directory format of
`electron-builder`: https://github.com/electron-userland/electron-builder#two-packagejson-structure
* Step 2: add build directory with icon files for mac / windows
* Step 3: move all development (web) assets into main directory
* Step 4: add `build` namespace to dev `package.json`
* Step 5: move all dev dependencies into dev file and get rid of
old electron packagers in favor of `eletorn-builder`
* Step 6: target build inside `app/` as everything else is excluded at build time
* Step 7: remove old stuff!
* Step 8: update README
* turn off asar for `child_pty`
