fix: add tiktoken as explicit dependency and document Rust requirement (#1826)

* feat: add tiktoken as explicit dependency and document Rust requirement

- Add tiktoken>=0.8.0 as explicit dependency to ensure pre-built wheels are used
- Document Rust compiler requirement as fallback in README.md
- Addresses issue #1824 tiktoken build failure

Co-Authored-By: Joe Moura <joao@crewai.com>

* fix: adjust tiktoken version to ~=0.7.0 for dependency compatibility

- Update tiktoken dependency to ~=0.7.0 to resolve conflict with embedchain
- Maintain compatibility with crewai-tools dependency chain
- Addresses CI build failures

Co-Authored-By: Joe Moura <joao@crewai.com>

* docs: add troubleshooting section and make tiktoken optional

Co-Authored-By: Joe Moura <joao@crewai.com>

* Update README.md

---------

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: Joe Moura <joao@crewai.com>
Co-authored-by: João Moura <joaomdmoura@gmail.com>

README.md

@@ -85,7 +85,6 @@ First, install CrewAI:
 ```shell
 pip install crewai
 ```
-
 If you want to install the 'crewai' package along with its optional features that include additional tools for agents, you can do so by using the following command:
 
 ```shell
@@ -93,6 +92,22 @@ pip install 'crewai[tools]'
 ```
 The command above installs the basic package and also adds extra components which require more dependencies to function.
 
+### Troubleshooting Dependencies
+
+If you encounter issues during installation or usage, here are some common solutions:
+
+#### Common Issues
+
+1. **ModuleNotFoundError: No module named 'tiktoken'**
+   - Install tiktoken explicitly: `pip install 'crewai[embeddings]'`
+   - If using embedchain or other tools: `pip install 'crewai[tools]'`
+
+2. **Failed building wheel for tiktoken**
+   - Ensure Rust compiler is installed (see installation steps above)
+   - For Windows: Verify Visual C++ Build Tools are installed
+   - Try upgrading pip: `pip install --upgrade pip`
+   - If issues persist, use a pre-built wheel: `pip install tiktoken --prefer-binary`
+
 ### 2. Setting Up Your Crew with the YAML Configuration
 
 To create a new CrewAI project, run the following CLI (Command Line Interface) command: