Fix readall and isexecutable deprecations

[jdlangs]

Switching isexecutable to isfile was mentioned previously here: JuliaLang/julia#12819 (comment)

It would also be nice to get a new tagged release as the current one predates the release of 0.4 and is stuffed with deprecation warnings.

Thanks,
Josh

[tkelman]

readstring needs to use the latest tag of Compat to work on release julia

[jdlangs]

I don't understand. An unversioned Compat in REQUIRE will not select the most recent version for 0.4?

[tkelman]

Right but if some other package were to ever put an upper bound on Compat (unlikely but possible), an unversioned requirement would not flag a conflict but would break here. Best to version the lower bound to be on the safe side.

[tkelman]

The Travis failure is expected since Travis obviously doesn't have Matlab. I adjusted the settings to "only build if .travis.yml is present." We could maybe try something with the redistributable Matlab Compiler Runtime if that could be made to work, but would have to check the license very carefully for whether that's permitted usage.

With a minimum version bound on Compat in REQUIRE I think this would be good to merge.

[jdlangs]

Fair enough for the versioning. Should be good to go now.

If it's desirable to have more widespread use of Compat versioning, it would probably be good for the docs to mentioned which tag each feature was introduced in.

[tkelman]

Yes good idea, that's worth a doc issue in Compat.