add support for all ITM packet types and replace Decoder with Stream parser

as this is a breaking change and requires a minor version bump, this commit
also:

- sets MSRV to 1.31.0
- changes the crate edition to 2018
- removes `itmdump`

Author: japaric

.gitignore

@@ -1,3 +1,4 @@
 *.rs.bk
 .#*
+Cargo.lock
 target

.travis.yml

@@ -4,6 +4,8 @@ matrix:
   include:
     - env: TARGET=x86_64-unknown-linux-gnu
       if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
+      # MSRV
+      rust: 1.31.0
 
 before_install:
   - set -e