feat(directive): ng:keypress New directives for binding to keypress eve...

[marknadig]

Original PR included on keyup/down. A number of comments suggested need for keypress.#1035 (comment)

[pkozlowski-opensource]

• Contributor signed CLA now or in the past (if you just signed, leave a comment here with your real name for cross reference)
• Feature improves existing core functionality
• API is compatible with existing Angular apis and relevant standards (if applicable)
• PR doesn't contain a breaking change
• PR contains unit tests
• PR contains e2e tests (if suitable)
• PR contains documentation update
• PR passes all tests on Travis (sanity)
• PR passes all tests on ci.angularjs.org (cross-browser compatibility)
• PR is rebased against recent master
• PR is squashed into one commit per logical change
• PR's commit messages are descriptive and allows us to autogenerate release notes (required [commit message

[IgorMinar]

lgtm

[pkozlowski-opensource]

@digger69 I've slightly changed the commit message and landed it as f20646b. Thank you!