Fixed title (PHP-FFMpeg#342)

Update of the README (PHP-FFMpeg#315)

Concat (PHP-FFMpeg#309)

* Fixed the way to throw an exception when we open the file in the Concat media.

Added a getAsBase64() method to Frame object (PHP-FFMpeg#292)

* Added a getAsBase64() method to Frame object
* Merged the getBase64 method in save method
* Differentiate the two possible return
* Corrected typo (Edited from github)

Improvements (PHP-FFMpeg#286)

* Adding a missing use statement in src/FFMpeg/Filters/Video/ExtractMultipleFramesFilter.php
* We remove a user specific folder from the gitignore
* We remove an unused use statement from src/FFMpeg/Filters/Video/ExtractMultipleFramesFilter.php
* We remove an unused use statement from src/FFMpeg/Filters/Video/PadFilter.php
* We remove an unused use statement from src/FFMpeg/Media/Waveform.php
* We remove an unused variable from src/FFMpeg/Filters/Waveform/WaveformDownmixFilter.php
* We fix the name of a variable in src/FFMpeg/Filters/Audio/AddMetadataFilter.php

Merge pull request PHP-FFMpeg#283 from Romain/multipleframes

Creation of a filter to extract multiple frames in one encoding session

Update changelog

Update changelog

Update changelog

Prepare version 0.5.0