add sfoundryup readme to seismic branch (was only on ameyas) (#41)

sfoundryup/README.md

@@ -14,3 +14,33 @@ To install the **nightly** version of Seismic Foundry tools:
 ```bash
 sfoundryup
 ```
+
+### Install a specific **version** (in this case the nightly version):
+```bash
+sfoundryup --version nightly
+```
+### Install a specific **branch** (in this case the seismic branch):
+```bash
+sfoundryup --branch seismic
+```
+### Install a **fork's main branch** (in this case YourUser/seismic-foundry's main branch):
+```bash
+sfoundryup --repo YourUser/seismic-foundry
+```
+### Install a **specific branch in a fork** (in this case the custom-branch branch's latest commit in YourUser/seismic-foundry):
+```bash
+sfoundryup --repo YourUser/seismic-foundry --branch custom-branch
+```
+### Install a **specific Pull Request**:
+```bash
+sfoundryup --pr 123
+```
+### Install from a **specific commit**:
+```bash
+sfoundryup -C abcdef1234567890
+```
+### Install from a **local directory or repository** (e.g., one located at ~/git/seismic-foundry, assuming you're in the home directory):
+```bash
+sfoundryup --path ./git/seismic-foundry
+```
+**Tip**: All flags have a single-character shorthand equivalent! You can use -v instead of --version, etc.