Add breaking changes and release 1.0.0.

Add breaking changes and release 1.0.0.

This makes `.error()` default to empty spans rather than
single-character ones. This better represents the semantics of failing
at a particular position in the text.

It also makes `lastMatch` reset whenever the scanner's position changes.
This makes `.error()` behave more consistently when primarily doing
character-based scanning, since it won't unexpectedly emit an error for
stale match data.

R=jmesserly@google.com

Committed: https://github.com/dart-lang/string_scanner/commit/42cb2dcd76ad8e613847af5e983cab73df1094a4

[Jennifer Messerly, 2016-06-10 00:48:11]

1.0 LGTM!

[nweiz, 2016-06-14 23:21:26]

Description was changed from

==========
Add breaking changes and release 1.0.0.

This makes `.error()` default to empty spans rather than
single-character ones. This better represents the semantics of failing
at a particular position in the text.

It also makes `lastMatch` reset whenever the scanner's position changes.
This makes `.error()` behave more consistently when primarily doing
character-based scanning, since it won't unexpectedly emit an error for
stale match data.

R=jmesserly@google.com
==========

to

==========
Add breaking changes and release 1.0.0.

This makes `.error()` default to empty spans rather than
single-character ones. This better represents the semantics of failing
at a particular position in the text.

It also makes `lastMatch` reset whenever the scanner's position changes.
This makes `.error()` behave more consistently when primarily doing
character-based scanning, since it won't unexpectedly emit an error for
stale match data.

R=jmesserly@google.com

Committed:
https://github.com/dart-lang/string_scanner/commit/42cb2dcd76ad8e613847af5e98...
==========

[nweiz, 2016-06-14 23:21:28]

Committed patchset #1 (id:1) manually as
42cb2dcd76ad8e613847af5e983cab73df1094a4 (presubmit successful).