Fix typo in typer target in Makefile

The typer target now works.
Use deps directory to trigger get-deps

A `make distclean` now removes the deps directory and all of its
contents. The default target now looks for the presence of the deps
directory to determine if `rebar get-deps compile` should be run. The
main benefit being that one can now do: `make distclean && make`
without a call to `make get-deps`. The get-deps target is left in
place for convenince and back compat.

The get-deps target was updated slightly to run get-deps and compile
as part of a single command. This should be slightly more efficient.
Make proper and neotoma dev-only dependencies

This patch makes erlware_commons easier to include as a dependency by
removing depedencies that are not needed at run time.

The top-level Makefile creates a .DEV_MODE marker file which is
detected by rebar.config.script. When the marker file is present, the
development only dependencies proper and neotoma are included and a
macro 'DEV_ONLY' is defined. The macro is used to only enable the
proper tests for development mode.

The ec_semver_parser.peg is now located in priv/ and is moved into
src/ by the Makefile. The generated ec_semver_parser.erl is now under
version control; it need not be rebuilt by all projects wishing to
include erlware_commons. It will be rebuilt, as before this change, on
every make invocation.
Merge pull request #39 from seth/sf/soft-dep-neotoma

Make proper and neotoma development-time only dependencies