Include information on pip-based installation

Fixes #7

README.md

@@ -41,6 +41,22 @@ Efficient MS/MS spectrum processing and visualization in Python.
 
 Missing dependencies will be automatically installed when you install `spectrum_utils`.
 
+### Alternative installation options
+
+The recommended way to install `spectrum_utils` is using conda. Alternatively `spectrum_utils` can also be installed using pip:
+
+```pip install spectrum_utils```
+
+To install the basic `spectrum_utils` version. Or:
+
+```pip install spectrum_utils[iplot]```
+
+To include the interactive plotting functionality (requires Pandas and Altair).
+
+When installing using pip it is recommended to explicitly install any dependencies (listed above or in the [environment file](environment.yml)) in advance. Any missing dependencies will be automatically installed from PyPI when you install `spectrum_utils`, _except_ RDKit. Please refer to the [RDKit installation notes](https://www.rdkit.org/docs/Install.html) for information on how to install RDKit.
+
+In contrast, when installing `spectrum_utils` using conda all dependencies will be automatically installed, including RDKit.
+
 ## Example
 
 ```