Switch travis email notifications back to the default.

Emails now go to author (+comitter).

 .travis.yml                  | 14 ++++----------
 build-support/bin/ci-sync.sh |  5 +++--
 2 files changed, 7 insertions(+), 12 deletions(-)

Testing Done:
$ travis lint
Hooray, .travis.yml looks valid :)

And CI went green here: https://travis-ci.org/pantsbuild/pants/builds/38073663

I enabled ci for my pantsbuild/pants fork and I added a commit of this:
```console
$ cat << EOF > build-support/bin/ci.sh
#!/usr/bin/env bash
exit 1
EOF
```
That CI went red and emailed just me for both the pantsbuild/pants and jsirois/pants jobs:
  https://travis-ci.org/jsirois/pants/builds/38087136

Email to just me:
 jsirois / pants (jsirois/travis/email_simple)

Build pantsbuild#4 is still failing.	 38 seconds
	John Sirois	f727f99 Changeset →
 	Small workding fixes.

Bugs closed: 682

Reviewed at https://rbcommons.com/s/twitter/r/1169/

.travis.yml

@@ -4,9 +4,6 @@ python:
   - "2.6"
   - "2.7"
 
-jdk:
-  - openjdk7
-
 install:
   - pip install coveralls
 
@@ -28,13 +25,10 @@ script: |
   java -version
   ./build-support/bin/ci.sh -d
 
-notifications:
-  email:
-    - [email protected]
-    - [email protected]
-    - [email protected]
-    - [email protected]
-    - [email protected]
+# We accept the default travis-ci email author+comitter notification
+# for now which is enabled even with no `notifications` config.
+# notifications:
+#   email: ...
 
 after_success:
   coveralls

build-support/bin/ci-sync.sh

@@ -54,8 +54,9 @@ with open('.travis.yml') as fp:
   config_linux = yaml.safe_load(fp)
 with open('.travis.osx.yml') as fp:
   config_osx = yaml.safe_load(fp)
-# We maintain notifications mailing lists centrally in the main '.travis.yml' config.
-config_osx['notifications'] = config_linux['notifications']
+# We maintain notification settings centrally in the main '.travis.yml' config.
+if 'notifications' in config_linux:
+  config_osx['notifications'] = config_linux['notifications']
 with open('.travis.yml', 'w') as fp:
   yaml.safe_dump(config_osx, fp)
 EOF