Fix tests/README (adapt to meson), use MD format

Resolves: #381

Signed-off-by: Sergio Arroutbi <[email protected]>

tests/README

@@ -0,0 +1 @@
+README.md

tests/README.md

@@ -0,0 +1,18 @@
+Tests are currently available for two different software token implementations,
+NSS's softokn and softhsm (with some limitations).
+
+The easiest way to configure things to run manual tests is to simply execute next command from project's root directory:
+```bash
+meson test -C build
+```
+Be aware that previous command might change if a different build directory has been selected. Previous command will create two temporary directories with each token's configurations.
+
+After `meson test` command has run, set up the environment with:
+```bash
+$ source tests/tmp.<softokn|softhsm>/testvars
+```
+
+Then code can be executed like:
+```bash
+$ openssl pkey -in $ECPUBURI -pubin -pubout -out ecout.pub
+```