docs(README.md and CONTRIBUTING.md): fix a few instruction issues (#814)

* docs(README.md): add pyproj to list of dependencies

Add pyproj to the list of dependencies in README.md, as it was missing.

* docs(CONTRIBUTING.md): correct nosetests command

* The command `nosetests -v t*_test.py` would not run (at least on Windows). I believe the command `nosetests -v` does what needs to be done.

* Also added a note about FloPy dependencies for tests to pass.

CONTRIBUTING.md

@@ -73,9 +73,9 @@ Before you submit your Pull Request (PR) consider the following guidelines:
     ```shell
     cd autotest
     nosetests -v build_exes.py
-    nosetests -v t*_test.py
+    nosetests -v
     ```
-   Note: the FloPy test suite requires the [nosetests](https://pypi.org/project/nose/) and [pymake](https://github.com/modflowpy/pymake) python packages.
+   Note: the FloPy test suite requires the [nosetests](https://pypi.org/project/nose/) and [pymake](https://github.com/modflowpy/pymake) python packages. All the FloPy dependencies must also be installed for the tests to pass.
 
 1. Commit your changes using a descriptive commit message that follows our
   [commit message conventions](#commit). Adherence to these conventions

README.md

@@ -190,6 +190,7 @@ Additional dependencies to use optional FloPy helper methods are listed below.
 | `.export(*.asc)` in `flopy.utils.reference` `SpatialReference` class                 | **scipy.ndimage**                                  |
 | `.interpolate()` in `flopy.utils.reference` `SpatialReference` class                 | **scipy.interpolate**                              |
 | `.interpolate()` in `flopy.mf6.utils.reference` `StructuredSpatialReference` class   | **scipy.interpolate**                              |
+| `._parse_units_from_proj4()` in `flopy.utils.reference` `SpatialReference` class     | **pyproj**                                         |
 | `.get_dataframes()` in `flopy.utils.mflistfile` `ListBudget` class                   | **pandas** >= 0.15                                 |
 | `.get_dataframes()` in `flopy.utils.observationfile` `ObsFiles` class                | **pandas** >= 0.15                                 |
 | `.get_dataframes()` in `flopy.utils.sfroutputfile` `ModflowSfr2` class               | **pandas** >= 0.15                                 |