Update README.md
added note about stale branches
Merge pull request #1214 from ErikZalm/Marlin_v1

added note about stale branches
Merge pull request #1213 from ErikZalm/Marlin_v1

added note about stale branches
Merge pull request #1215 from ErikZalm/Marlin-v1-bug-fixing

Merge pull request #1214 from ErikZalm/Marlin_v1
Merge pull request #1216 from ErikZalm/Marlin-v1-stable

Merge pull request #1213 from ErikZalm/Marlin_v1
Merge commit 'dc64175d77dde61f67276ff1f8bbc3f52a252836' into Marlin_phoenix

* commit 'dc64175d77dde61f67276ff1f8bbc3f52a252836':
  Update README.md
Merge commit 'b792b740365f4bb99da87686ea7735b40bb8a969' into Marlin_phoenix

* commit 'b792b740365f4bb99da87686ea7735b40bb8a969':
  added note about stale branches
Merge commit '203df3533d153b6c455e44f3482a173ec835199f' into Marlin_phoenix

* commit '203df3533d153b6c455e44f3482a173ec835199f':
Merge commit 'af7fbcc026fcfceb33a9232dbf699acb5d80ba11' into Marlin_phoenix

* commit 'af7fbcc026fcfceb33a9232dbf699acb5d80ba11':
Merge commit 'fe8d8beb7a9c5288a0fe4beb32bbf32bf93e923e' into Marlin_phoenix

* commit 'fe8d8beb7a9c5288a0fe4beb32bbf32bf93e923e':