Version bumps (#5479)

* bump platform.txt back to 2.5.0-dev

* bump README.md to 2.5.0-beta1

Author: devyte

Diff for: README.md

@@ -3,7 +3,7 @@ Arduino core for ESP8266 WiFi chip
 
 # Quick links
 
-- [Latest release documentation](https://arduino-esp8266.readthedocs.io/en/2.4.2/)
+- [Latest release documentation](https://arduino-esp8266.readthedocs.io/en/2.5.0-beta1/)
 - [Current "git version" documentation](https://arduino-esp8266.readthedocs.io/en/latest/)
 - [Install git version](https://arduino-esp8266.readthedocs.io/en/latest/installing.html#using-git-version) ([sources](doc/installing.rst#using-git-version))
 
@@ -36,7 +36,7 @@ Starting with 1.6.4, Arduino allows installation of third-party platform package
 #### Latest release [![Latest release](https://img.shields.io/github/release/esp8266/Arduino.svg)](https://github.com/esp8266/Arduino/releases/latest/)
 Boards manager link: `http://arduino.esp8266.com/stable/package_esp8266com_index.json`
 
-Documentation: [https://arduino-esp8266.readthedocs.io/en/2.4.2/](https://arduino-esp8266.readthedocs.io/en/2.4.2/)
+Documentation: [https://arduino-esp8266.readthedocs.io/en/2.5.0-beta1/](https://arduino-esp8266.readthedocs.io/en/2.5.0-beta1/)
 
 ### Using git version (basic instructions)
 [![Linux build status](https://travis-ci.org/esp8266/Arduino.svg)](https://travis-ci.org/esp8266/Arduino)
@@ -113,7 +113,7 @@ Please provide as much context as possible:
 
 For minor fixes of code and documentation, please go ahead and submit a pull request.
 
-Check out the list of issues which are easy to fix — [easy issues for 2.5.0](https://github.com/esp8266/Arduino/issues?q=is%3Aopen+is%3Aissue+milestone%3A2.5.0+label%3A%22level%3A+easy%22). Working on them is a great way to move the project forward.
+Check out the list of issues which are easy to fix — [easy issues pending](https://github.com/esp8266/Arduino/issues?q=is%3Aopen+is%3Aissue+label%3A%22level%3A+easy%22). Working on them is a great way to move the project forward.
 
 Larger changes (rewriting parts of existing code from scratch, adding new functions to the core, adding new libraries) should generally be discussed by opening an issue first.
 

Diff for: platform.txt

@@ -5,8 +5,8 @@
 # For more info:
 # https://github.com/arduino/Arduino/wiki/Arduino-IDE-1.5---3rd-party-Hardware-specification
 
-name=ESP8266 Boards (2.5.0-beta1)
-version=2.5.0-beta1
+name=ESP8266 Boards (2.5.0-dev)
+version=2.5.0-dev
 
 runtime.tools.xtensa-lx106-elf-gcc.path={runtime.platform.path}/tools/xtensa-lx106-elf
 runtime.tools.esptool.path={runtime.platform.path}/tools/esptool