Bump version for new release

[LKedward]

PR to bump version to 0.2.0.

I'll create the new release on github once merged. See below for proposed change log entry, feel free to edit.

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Changes:

• Replace deprecated flags in gfortran debug profile (Replace deprecated flags in debug_fortran option #386)

• --release flag is replaced by --profile release (Implement --flag option for Fortran fpm #390)

• Programs can use modules defined in relative subdirectories (Give Programs Access to Code in Subdirectories #409)

New features:

• Add support for specifying an include directory (Add explicit include-dir key to manifest #377)

• Implement --flag command line option (Implement --flag option for Fortran fpm #390)

Fixes:

• Fix problems when building with local paths (problems with building with local paths #327,Implement --flag option for Fortran fpm #390)

• Fix for executable link libraries when auto discovery is enabled (Minor fix: for setting executable link libraries. #398)

• Fix fpm_strings::join for null inputs (correct join for null input #404)

[awvwgk]

You beat me by a minute here. Looks good to go.