More clear error messages for invalid characters

[pforhan]

Tweaks invalid start- and end-of-token messages for clarity.

Inspired by #33, fixes #32 and fixes #34, probably #29 as well.

[pforhan]

Not sure what's up with the CI build, a ./gradlew clean build comes back successful for me.

[pforhan]

ci says:

failed to find target with hash string 'android-23' in: /usr/local/android-sdk

[zach-klippenstein]

LGTM 👌

[pforhan]

Pushed a small change to help users differentiate the first-character message from the error later on.

[pforhan]

@JakeWharton @rjrjr @loganj anyone interested in merging this?

[rjrjr]

LGTM, but can we figure out why the Travis is failing?

[pforhan]

I think this is it:

Package Android SDK Platform-tools, revision 26 not installed due to rejected license 'android-sdk-license-c81a61d9'.

[pforhan]

That passed. Pushed a small formatting fix for the .travis.yml file

[pforhan]

Sigh, and another -- I added the newline to the wrong place

[pforhan]

Green!

[pforhan]

Can I get a merge here? I think this is a good usability improvement that will head off more issues like #36