When installing CLIP via pip on Python 3.10+ systems with setuptools 71+, the installation fails with: ModuleNotFoundError: No module named 'pkg_resources'

## Problem

When installing CLIP via pip on Python 3.10+ systems with setuptools 71+, the installation fails with:
```
ModuleNotFoundError: No module named 'pkg_resources'
```

pip creates an **isolated build environment** in a temporary directory when building packages from source. In this isolated environment, setuptools is installed fresh — and in newer versions (71+), `pkg_resources` is no longer automatically available as a top-level importable module within that subprocess context, even though setuptools itself is present.

The original `setup.py` imported `pkg_resources` at the module level and used `pkg_resources.parse_requirements()` to read `requirements.txt`. Since this code runs inside pip's isolated build subprocess, it fails before the wheel can even be built — making CLIP completely uninstallable from source on modern systems without workarounds.

Closes #532

## What Changed

**Before:**
```python
import pkg_resources

install_requires=[
    str(r)
    for r in pkg_resources.parse_requirements(
        open(os.path.join(os.path.dirname(__file__), "requirements.txt"))
    )
]
```

**After:**
```python
install_requires=[
    stripped
    for line in open(os.path.join(os.path.dirname(__file__), "requirements.txt"))
    for stripped in [line.strip()]
    if stripped and not stripped.startswith("#")
],
```

- Removed the `pkg_resources` import entirely
- Replaced `parse_requirements()` with plain Python file I/O
- Strips each line before checking for blank/comment — so lines like `"  # comment"` are correctly excluded (previous version missed these)
- Properly indented inside `install_requires`

## Impact

- Fixes installation on any system running setuptools 71+
- Tested on Python 3.10.19, setuptools 82.0.1
- No behavior change for existing users
- Removes the only legacy `pkg_resources` dependency from `setup.py`
- Makes the build process more robust and future-proof

Author: Aadi775

setup.py

@@ -1,6 +1,4 @@
 import os
-
-
 from setuptools import setup, find_packages
 
 setup(
@@ -11,9 +9,10 @@
     author="OpenAI",
     packages=find_packages(exclude=["tests*"]),
     install_requires=[
-        line.strip()
+        stripped
         for line in open(os.path.join(os.path.dirname(__file__), "requirements.txt"))
-        if line.strip() and not line.startswith("#")
+        for stripped in [line.strip()]
+        if stripped and not stripped.startswith("#")
     ],
     include_package_data=True,
     extras_require={'dev': ['pytest']},