fix escaping for no pex file, no pants executable error messages

This changes messages with substitutions to make sure all single quotes are escaped by doubling them.

IntelliJ uses MessageFormat[1] when a bundled message contains `{`. `{0}` means insert the first argument here in MessageFormat's pattern language. Single quotes are used for escaping, so `'{0}'` is rendered as `{0}`. Double single quotes `''`, are escaped single quotes. Unpaired single quotes are discarded.

The thing this fixes is that `couldn't blah '{0}'` would render as `couldnt blah arg`. The intended string was `couldn't blah 'arg'`. What was happening was that the characters between the contraction's apostrophe and the first single quote of `'{0}'` were treated as a quoted string, and the last quote was discarded resulting in the unexpected message.

 1. http://docs.oracle.com/javase/7/docs/api/java/text/MessageFormat.html

Testing Done:
Ran tests, ran an intellij instance w/ misconfigured pex, pants to see message changes.

Reviewed at https://rbcommons.com/s/twitter/r/1246/
update readme w/ typo fixes, code highlighting, copy adjustments

Reviewed at https://rbcommons.com/s/twitter/r/1247/